CN101213461A

CN101213461A - Methods and systems for detecting a capacitance using SIGMA-DELTA measurement techniques

Info

Publication number: CN101213461A
Application number: CN200680019492.2A
Authority: CN
Inventors: J·K·雷诺; K·哈格里夫斯; D·埃利; P·鲁特利; A·多伊格; J·海恩斯
Original assignee: Synaptics Inc
Current assignee: Synaptics Inc
Priority date: 2005-06-03
Filing date: 2006-06-02
Publication date: 2008-07-02
Anticipated expiration: 2026-06-02
Also published as: CN101273274A; CN101213461B; CN101283507B; CN101283507A

Abstract

Methods, systems and devices are described for detecting a measurable capacitance (Cx) using sigma-delta measurement techniques. According to various embodiments, a voltage is applied to the measurable capacitance (Cx) using a first switch. The measurable capacitance is allowed to share charge with a passive network. If the charge on the passive network (109) is past a threshold value, then the charge on the passive network (109) is changed by a known amount for a sufficient number of repetitions until the measurable capacitance (Cx) can be detected. Such a detection scheme may be readily implemented using conventional components, and can be particularly useful in sensing the position of a finger, stylus or other object with respect to a button, slider, touchpad or other input sensor.

Description

Use the SIGMA-DELTA measuring technique to detect the method and system of electric capacity

Right of priority

[0001] the application requires the U.S. Provisional Patent Application No.60/687 of submission on June 3rd, 2005,012,60/687,166,60/687,148,60/687,167,60/687,039 and 60/687,037 reach the No.60/774 that submits on February 16th, 2006,843 right of priority, they are introduced into as a reference at this.

Technical field

[0002] the present invention relates generally to capacitance detecting, relate more specifically to use SIGMA-DELTA type measuring technique can detect equipment, the system and method that to measure electric capacity.

Background technology

[0003] capacitive transducer that response taken place for electric charge, curtage can be used for the detection position or close on (perhaps motion or existence or any similar information), and usually as computing machine, PDA(Personal Digital Assistant), media player, video game machine, consumption electronic product, cell phone, coin telephone, point of sales terminal, the talk input equipment of mechanical, electrical public telephone booth etc. automatically.In user's load button, slip control, rolling ring, rolling band and other type sensor, use capacitive transducer.One of employed capacitive transducer type is the button-type sensor in this application, and it can be used to provide the information that occurs or exist about input.The another kind of type of employed capacitive transducer is the touch-pad type sensor in this application, it can be used to provide the information about input, such as position, motion and/or along the similar information of (1-D sensor), diaxon (2-D sensor) or multiaxis.The other information that provides also selectively is provided for button-type and touch-pad type sensor, for example some indications of the acting force that is associated with input, duration or capacitive coupling amount.In U.S. Patent No. 5,880, an example based on the 2-D touch-pad type sensor of capacitance detecting technology has been described in 411, this patent licenses to Gillespie etc. on March 9th, 1999.For example, this sensor can find in the input equipment of electronic system easily that this electronic system comprises hand-held and notebook computer.

[0004] usually, the user is usually by placing one or more finger, contact pilotage and/or object or move near being arranged on the input equipment or the sensitive zones of one or more sensors of input equipment comes the operation of capacitor input equipment.This is in application on the carrier signal of sensitive zones and produces capacity effect, and described carrier signal can be detected and be associated with respect to the positional information of sensitive zones (for example position or close on or motion or existence or similar information) with stimulation/excitation.Next, this positional information can be used for selecting, move, roll or operates in text on the display screen, figure, cursor and the highlighted and/or combination in any of other designator arbitrarily.This positional information also can be used can make user and interface alternation effect, for example controls volume, adjusts brightness or realizes other purpose arbitrarily.

[0005] although capacitive transducer has been widely used for many years, the sensor designer continues to seek the method that improves sensor function and efficient.Particularly, the slip-stick artist is not increasing design and the embodiment of making great efforts to simplify position transducer under the condition of cost unceasingly.In addition, because increase day by day, so the demand of and sensor design scheme that easily implement low-cost again occurred to high flexibility in the demand of all kinds electronic equipment to this sensor.Particularly, occurred dirigibility is enough to be used in various embodiments and has enough abilities that the accurate capacitance detecting needs of the sensor design scheme of retained costs benefit simultaneously are provided.

[0006] therefore, be desirable to provide fast, effectively and efficient detection can measure the system and method for electric capacity.In addition, wish to create a kind of design proposal of using the element that obtains easily to implement easily, the described element that obtains easily is IC standard, microcontroller and discrete elements for example.According to detailed subsequently instructions and appended sharp claim, with aforementioned technical field and background, the characteristics of other hope and characteristic will become apparent in conjunction with the accompanying drawings.

Brief overview

[0007] describe use SIGMA-DELTA measuring technique and be used to detect method, system and the equipment that can measure electric capacity, described SIGMA-DELTA measuring technique need not to require inner active analog element just can carry out on many standard microcontrollers.According to various embodiment, use first switch to apply voltage to measuring electric capacity.Permission can be measured electric capacity and be shared electric charge with passive network.If the electric charge on the passive network surpasses threshold value, then the electric charge on the passive network is changed scheduled volume, and repeats this process.The result that charge threshold detects is the measures of quantization to electric charge, can carry out filtering to produce the measured value of measurable electric capacity to it.This detection scheme can use the element that obtains easily and easily implement, and can specifically be applied in and detect finger, contact pilotage or other object position, this capacitive transducer executive button function, sliding function, cursor control or user interface navigation function or other function arbitrarily with respect to capacitive transducer.

Brief description of the drawings

[0008] below, various aspects of the present invention will be described in conjunction with accompanying drawing subsequently, wherein same numeral same parts, and

[0009] Figure 1A shows the block diagram of typical first order SIGMA-DELTA detection technique, and Figure 1B is the typical sequential chart of embodiment shown in Figure 1A;

[0010] Fig. 2 is the process flow diagram of typical SIGMA-DELTA capacitance detecting technology;

[0011] Fig. 3 A-B is typical SIGMA-DELTA capacitive detection circuit figure, and it uses three digital incoming/outgoing pin of passive network and controller to realize that Fig. 3 C is typical time-scale, and Fig. 3 D is the typical sequential chart of exemplary embodiments shown in Fig. 3 A;

[0012] Fig. 4 A-B is typical SIGMA-DELTA capacitive detection circuit figure, and it uses two digital incoming/outgoing pin of passive network and controller to realize that Fig. 4 C is typical time-scale, and Fig. 4 D is the typical sequential chart of embodiment shown in Fig. 4 A;

[0013] Fig. 5 A is typical SIGMA-DELTA capacitive detection circuit figure, and it uses a digital incoming/outgoing pin of passive network and controller to realize that Fig. 5 B is typical time-scale, and Fig. 5 C is the typical sequential chart of embodiment shown in Fig. 5 A;

[0014] Fig. 6 A-B is replaceable typical SIGMA-DELTA capacitive detection circuit figure, and it uses the I/O pin of passive network and digitial controller to implement many sense channels;

[0015] Fig. 7 A is typical multielectrode sensor figure, and it is included in the DELTA capacitor of sharing between the sense channel, and Fig. 7 B is the status switch table of being correlated with;

[0016] Fig. 8 A is to use the typical case of SIGMA-DELTA technology implementation to connect to change electric capacity (transcapacitive) sensor figure, and Fig. 8 B is the status switch table of being correlated with, the typical case that the SIGMA-DELTA technology that is to use Fig. 8 C realizes is parallel to change capacitive transducer figure, and Fig. 8 D is the status switch table of being correlated with;

[0017] Fig. 9 A-B is the circuit diagram that is used for reducing at capacitive detection system the representative configuration of power supply noise influence; With

[0018] Figure 10 is the synoptic diagram with approaching sensor equipment of electronic system.

Describe in detail

[0019] detailed instructions in fact only is exemplary below, and is not used in restriction the present invention or the application and use of the present invention.In addition, intention do not lie in by aforementioned technical field, background, brief overview or below theoretical constraint the expressed or that imply in the detail specifications.

[0020], use the SIGMA-DELTA modulation technique can easily make up capacitance detecting and/or metering circuit according to various exemplary embodiments.Usually, term " SIGMA-DELTA " relates to the simulation digital transition scheme extremely that quantizes electrical effect (for example electric capacity) in conjunction with electric charge summation (SIGMA) and differential (DELTA), and described electrical effect is showed by electrode or other electrical nodes.In the SIGMA-DELTA capacitance detecting, for example, analogue integrator accumulation usually shifts the electric charge of coming according to a plurality of electric charge failover events from measuring electric capacity.With also be applied in and preset the quantity from measuring other electric charge that electric charge that electric capacity receives has relative symbol, to keep near near the electric charge that gathers the known level.Just, from analogue integrator, extract the electric charge of quantized amount suitably, to keep wave filter output near ideal level.Be used for the quantity of the relative electric charge of integrator by association, can determine by measuring the quantity of electric charge that electric capacity shifts.Next, can use this capacitance to confirm finger, contact pilotage or other objects near the appearance of institute's detection node or do not occur, and/or be used for other purpose arbitrarily.Therefore, the SIGMA-DELTA scheme can be used in many distinct methods, to determine the electric capacity on present electrode or the analog.

[0021] in addition, (for example only use conventional trnasistion mechanism, the signal pin of opertaing device, discrete switch or the like), just realize following various embodiment easily, the input of numeric door need not to increase the extra active electronic equipment of cost and complexity as quantizer (it can also use the signal pin of opertaing device to be implemented) and passive element (for example one or more capacitors, resistance and/or analog).Therefore, use to obtain easily and the reasonable element of price, can conveniently in various environment, implement various schemes described here again reliably, as described more fully below.

[0022] turns to accompanying drawing and beginning with reference to Figure 1A now, but be used for determining Measurement of capacitor (C _X) 102 typical first order SIGMA-DELTA converter 100 comprises passive network 109, quantizer 110 (its can be comparer or if then it is the input of numeric door to quantizer of expectation), digital to analog converter 116 (it can be the switch to one or more voltage) and be used for allowing to measure electric capacity 102 and DELTA " reference " electric capacity (C _D) 126 suitably to the switch 106,122 of the suitable quantity of integrating capacitor 108 charging and discharge.

[0023] in this embodiment, passive network 109 is embodied as integrating capacitor 108 simply.Shown integrating capacitor 108 (C _I) utilize conventional capacitor to realize, described conventional capacitor is configured to have usually the incomplete integrator of big capacitance values, and described capacitance maybe can be measured the desired numerical value of electric capacity 102 obviously big (for example, one or more order of magnitude) greatly than the numerical value of DELTA electric capacity 126 usually.In each embodiment, for example, but measure electric capacity 102 and DELTA electric capacity 126 can be the picofarad level, and integrating capacitor 108 is the bicrofarad level, although other embodiment can be broadly in conjunction with the different numerical value that are used for specific capacitor.In conjunction with digital to analog converter voltage 118,120 and charging voltage 104, effectively DELTA electric capacity 126 determines to measure the scope of capacitance values.Also possible is puts upside down the electric capacity measured 102 among Fig. 1 and the role of DELTA electric capacity 126.In this case, will be transferred to integrating capacitor 108 to electric charge from DELTA electric capacity 126 by switch 106, and can to measure electric capacity 102 can be feedback capacity, this feedback capacity is shifted by switch 122 and by data 114 controls.This causes data output 114 and can measure electric capacity 102 inversely proportional, and is in direct ratio with DELTA electric capacity 126.Wherein in reciprocal mechanism, determine or the embodiment of signal that filtering occurs or noise in, this " reciprocal electric capacity " sensor is useful with respect to the direct proportion capacitive transducer.

[0024] can measure electric capacity 102 is the effective capacitances that have by any signal source, electrode or other electrical nodes of SIGMA-DELTA converter 100 detectable electron capacitance.In Figure 1A, can measure electric capacity 102 and be shown as variable condenser.For the input equipment of accepting input from one or more fingers, contact pilotage and/or other excitation (stimuli), can measure often total effective capacitance (" absolute capacitance ") of the local ground connection of expression of electric capacity 102 from detection node to system.The total effective capacitance that is used for input equipment can be quite complicated, relates to as electric capacity, resistance and inductance by sensor design and determined series connection of operating environment and parallel connection.In other situation, can measure electric capacity 102 and can represent total effective capacitance (" transformation electric capacity ") from the drive node to the detection node.This total effective capacitance is can also be quite complicated.Yet, in many cases, can be the small variable capacitance in parallel with the input simple analog with fixed background electric capacity.In any situation, impose at first with reference to the charging voltage 104 of local system ground connection and can measure electric capacity 102, as following more abundant described, allow to measure electric capacity 102 then and share by applying the electric charge that charging voltage 104 produces with passive network 109.

[0025] in the typical SIGMA-DELTA converter 100 shown in Figure 1A, can measure electric capacity 102 and be charged to charging voltage 104, and share electric charge with integrating capacitor 108 in response to the position of switch 106.Similarly, DELTA electric capacity 126 is charged to appropriate value (for example, low reference voltage 118 described below or high reference voltage 120), and is applied to integrating capacitor 108 via switch 122.Switch 106,122 responsive control signals 105,124 are set to proper states respectively, and described control signal 105,124 is for being suitable for switch 106,122 is set between when appropriate any electricity, logic or other signal of proper states.In various embodiments, switch 106,122 provides by the input/output signal pin of digital control circuit, the internal control signal that produces in control circuit of response and control this input/output signal pin suitably.In the simple concept embodiment shown in Fig. 1, control signal 105,124 is by symbol φ ₁, φ ₂Indicate.These control signals can be periodicity, acyclic, produce by steering logic and/or analog.In various embodiments, DELTA electric capacity 126 can be recharged and share to integrating capacitor 108 continuously for several times.This embodiment will allow relatively little DELTA electric capacity 126 to play very large effective capacitance effect.Just, the actual change (or " DELTA ") that imposes on the electric charge of integrating capacitor 108 numerical value by DELTA electric capacity 126 but also determine not only by the concrete steering logic that applied via switch 122 and the numerical value of reference voltage.

[0026] use any quantization device 110 or other simulation to numeral to change (ADC) technology, the electric charge that remains on the integrating capacitor 108 is changed into numeric data stream 114 suitably.In various embodiments, the input of simple comparator or numeric door provides an ADC output, and whether the input voltage of its indication integrating capacitor 108 is greater than or less than reference voltage (V _Cmp) 112.An ADC output is latched by control signal subsequently, for example the signal psi shown in Figure 1A-B ₁Although the simple examples quantizer 110 shown in Figure 1A provides logic " height " or " 1 " output when integrating capacitor voltage surpasses reference voltage 112, this transformation is elective to a certain extent; Therefore, under the situation of theory described here, alternative embodiment may provide logic " low " or " 0 " output under this situation.Can sample to the output that comes quantizer 110 with any usual manner (for example, using digital latch circuit 111), to keep the data stream 114 that is used for aftertreatment.

[0027] output data 114 expression can be stored by any way, filtering (for example, by digital filter 115), average, extract and/or any digital output set of other processing.Use many threshold values, stacked ADC level and/or use routine techniques etc., other embodiment can provide multidigit resolution.For example, can pass through more than a reference voltage (for example, a plurality of comparative voltage V _Cmp) threshold value is provided.This high-resolution output can be latched at one and locate constantly or be latched as a series of outputs (for example, as approaching one by one).Can also use the digital data stream 114 that provides by quantizer 110 and/or latch 111, with definite " DELTA " electric charge (same " ladder " electric charge) that will impose on the suitable quantity of integrating capacitor 108.A plurality of DELTA electric capacity same or different sizes can also be used to change the quantity that applies electric charge.In the exemplary embodiments shown in Figure 1A, for example, the voltage on logic high (" 1 ") the output 114 expression integrating capacitors 108 exceeds the situation of reference voltage 112, and indication should apply corresponding " DELTA " electric charge by DELTA electric capacity 126.Therefore, data output 114 can be used for selecting between " low " and " height " reference voltage 118,120, the perhaps quantized values of some between them changes (DAC) 116 with simple digital to the simulation that the electric charge that control applied by DELTA electric capacity 126 is provided.Replacedly, whether the electric charge (being reference charge) that can control on the DELTA electric capacity 126 of one or more data output 114 shares (arbitrary portion of for example, transferring to this integrating capacitor 108) with integrating capacitor 108.Therefore, in concrete data output 114, the electric charge on the DELTA electric capacity 126 can be shared zero degree, one or many.Owing to there is not electric charge to shift, is not similar to and sets DAC 116 output voltages and equal voltage on the integrating capacitor 108 so share (sharing zero degree).In any case, for the numerical value of data output 114, the effective charge of sharing is ignored.Therefore, this " feedback loop " of DAC 116, switch 122 and DELTA electric capacity 126 will provide suitable " DELTA " charge value to integrating capacitor 108, to offset by measuring the electric charge that electric capacity 102 imposes on integrating capacitor 108.In addition, because the quantity of the reference charge that applies is dose known amounts (based on the numerical value of DELTA electric capacity 126 and reference voltage 118,120), so can easily determine to impose on the total quantity of integrating capacitor 108 with feedback " DELTA " electric charge of the relative constant charge measurement of maintenance passive network 109 according to digital data stream 114.Just, digital data stream 114 represents to impose on the quantity of " DELTA " electric charge of integrating capacitor 108 suitably, and next this represent from measuring the electric charge that electric capacity 102 receives.By being associated with (filtering) and initially applying, can easily determine to measure electric capacity 102 from measuring amount of charge that electric capacity 102 receives to produce the voltage of this electric charge.

[0028] because the figure among Figure 1A is used as typical logical expressions, rather than the side circuit of capacitive transducer implements, therefore the concrete function shown in can be in various alternative embodiments by combination mutually, omit, strengthen or differently implement in addition.For example, comparer and numeral can use the one or more input/output signal pins on the microcontroller etc. to be implemented to simulating changing function 110,116, but and needn't use the identification circuit discrete or that separate shown in Figure 1A to realize.Usually need not extra active circuit and can easily realize quantizer 110, this is because many commercial available ASIC or microcontroller products provide cmos digital input, comparer or schmidt trigger function or the similar functions of the signal that is used for receiving on some input pin, perhaps in ASIC or microcontroller, allow the multiplexed of pin or function, for example ADC or DAC, although in certain embodiments, can also use outside multiplexer.In addition, this embodiment generally can implement filtering or other operation to the numerical data 114 that obtains, thereby by using the SIGMA-DELTA technology greatly to simplify the design of capacitive detection circuit.

[0029] the concrete Butut among Figure 1A combines the signal transition that DAC 116 wherein is squeezed, but integrating capacitor 108 and quantizer 110 do not have inverted notation convention.Although DELTA electric capacity 126 should offer " DELTA " on integrating capacitor 108 or opposite influence by measuring the electric charge that electric capacity 102 is supplied with, can apply this " inversion " in any way.Just, by adjusting the symbol or the amplitude of various reference signals 104,112,118,120, and/or, can make up any amount of replaceable but equivalent embodiment by adjusting various configuration of components shown in Figure 1A.Several examples of the side circuit that is suitable for detecting electric capacity have been described below.

[0030] can operate the essential characteristic shown in Figure 1A by any way.In an operative technique shown in Figure 1B, as by symbol φ ₁, φ ₂Two non-overlapped control signals that indicated trigger the electric charge transfer processing, this processing allows electric charge to be transferred to integrating capacitor 108 from measuring electric capacity 102, and be used for carrying out reverse charging from DELTA electric capacity 126, to adjust the charge level that keeps by integrating capacitor 108.This electric charge shifts with V shown in Figure 1B _X, V _IAnd V _DThe series voltage trace reflect, wherein on its each self-capacitance 102,108 and 126 with reference to V _X, V _IAnd V _DAs shown in FIG., respond low (" 0 ") data value 114, with V _DBe set at the height (" V among Figure 1A _H"), otherwise with V _DBe set at the low (" V among Figure 1A _L").When switch 122 is coupled to integrating capacitor 108, appropriate charge is transferred to integrating capacitor 108 from DELTA electric capacity 126, thereby at voltage V _IThe suitable variation of last generation.After initial start period, because negative feedback causes electric charge to be added to integrating capacitor 108 or from integrating capacitor 108 by DELTA electric capacity 126 and subdues, so voltage V _IWill be usually near comparator voltage V _Cmp

[0031] scope of measurable capacitance is by V _X, V _LAnd V _H, DELTA electric capacity 126 the number of times (N) that is fed of numerical value, each DELTA electric capacity 126 measuring period and can measure the number of times (M) that electric capacity 102 shares with passive network 109 each measuring period and determine.Be electric charge on the passive network 109 and the time between the threshold measuring period.For the first order, can measure the determined value of electric capacity 102 and (suppose that retentive control is to V _CmpVoltage V _I) at C _D(N/M) ((V _L-V _Cmp)/(V _X-V _Cmp)) and C _D(N/M) ((V _H-V _Cmp)/(V _x-V _Cmp)) between.As implied above, in many alternative embodiments, can change concrete notation convention and other certain operational parameters of being used for Figure 1A-B.

[0032] existing main reference Fig. 2 (but continuation) with reference to the architectural feature shown in the figure 1, the typical technology 200 that is used to carry out SIGMA-DELTA electric capacity sample detecting suitably comprises following key step: apply voltage (step 202) to measuring electric capacity 102, allow electric charge to be transferred to the passive network 109 (step 204) that comprises integrating capacitor 108, then based on the electric charge (step 210) on threshold value (step 206) the adjustment passive network from measuring electric capacity 102.Each that handle in each step in 200 is repeated the circulation (step 214) of suitable number, measures to allow accurate SIGMA-DELTA.

[0033] charge step 202 comprises suitably and uses any proper technology that known voltage is imposed on can to measure electric capacity 102.In each embodiment, if suitable, charging voltage (for example, low or high digital output, power supply signal and/or analog) 104 is applied in by excitation controller signal pin or other switch 106.Although should be noted in the discussion above that each switch in the converter 100 is illustrated with concrete arrangement, this only is a kind of example of arrangement.When should also be noted that in each embodiment " use " or " excitation " switch, this " use " or " excitation " can be implemented as and select Closing Switch, select to open the combination in any in switch or other energizing switch.Therefore, by layout, utilize arbitrary combination of closing or opening switch to apply voltage according to specific embodiments.In addition, in one or more pulses (for example, by repeatedly connecting and release-push 106), or by any other technology, charging voltage can at least once impose on can measure electric capacity 102.

[0034] after charging, permission can be measured electric capacity 102 and be shared electric charge with passive network 109, and described passive network 109 just almost can carry out integration and storage to electric charge without amplifier or other active component.In the embodiment that simplifies, passive network 109 only is an integrating capacitor 108, and it can be single capacitor; Replacedly, if suitable, passive network 109 can comprise arbitrary number resistance, capacitor and/or other passive element, and the example of a large amount of passive networks is described below.Share electric charge in order to allow to measure electric capacity 102 with passive network, shift outside (for example, not charging simultaneously), to allow electric charge without any need for action to measuring electric capacity except suspending the enough time.In each embodiment, time out can quite (for example be lacked, if being connected directly to, integrating capacitor 108 can measure electric capacity 102), some time delays may appear (for example perhaps, for electric charge, be arranged on the passive network 109 that to measure the one or more resistance elements between electric capacity 102 and the integrating capacitor 108 and shift) by having.In other embodiments, allowing the electric charge transfer to comprise encourages one or more switches (for example, the switch among Fig. 1 106) effectively or takes other action as if suitable words.In each embodiment, before taking further action, step 202 and/or step 204 can be repeated twice or repeatedly.

[0035] although should be noted in the discussion above that can measure electric capacity 102 can be coupled to filter capacitor still, the electric charge between the electric capacity is shared in the time of can being considered to start from substantially charge step 202 and finishing (for example, voltage is imposed on can measure electric capacity and finish time).In addition, it is enough approximate that the electric charge between the electric capacity is shared the voltage that can be considered to end at substantially on the electric capacity, and can ignore the electric charge of sharing the time.Electric charge is shared also can end to apply voltage haply next time, because (for example, the 104 chargings) voltage that applies accounts for leading.Thereby, even being coupled in the passive share system that can measure electric capacity at filter capacitor always, the Low ESR of the voltage source that applies makes can measuring the electric charge of sharing on the electric capacity and can ignore, and removes until the voltage that applies.

[0036] in the time will being transferred to passive network 109 effectively from the electric charge that can measure electric capacity 102, electric charge on the passive network 109 is measured (step 206) suitably, surpass appropriate threshold (step 208) if determine amount of charge, then the electric charge on the passive network 109 changes (step 210).Can implement charge measurement by any way.In various embodiments, on behalf of electric charge, the voltage on the passive network 109 obtain from I/O (I/O) pin or other equipment of microcontroller.In many this embodiment, the circuit that is associated with input pin can also analog to numeral (A/D) transformation maybe can be with voltage and the one or more threshold value V that records _THCompare, thus execution in step 206,208 effectively.Concrete threshold value V _TH(for example, reference voltage 112 is by the V that offers quantizer 110 among Fig. 1 _CmpRepresent) can be with embodiment significant change and slowly variation in time.In simple embodiment, the effect (1-position quantizer) of comparer is played in the cmos digital input, and it has the reference voltage of the threshold level that equals the numeral input.Quantizer 110 can directly maybe can be connected by multiplexer or other switching network with passive network.

[0037] have in the situation of hysteresis in input, Schmidt trigger is for example often usefully guaranteed the voltage ratio that records is being set at known state with hysteresis before, thereby is relatively provided similar threshold value to all.Replacedly, can use hysteresis is set at known state, reliably to select between the threshold value that relatively goes up in difference.This can finish by set input simply before the known numeric value of setting hysteretic state is compared.

[0038] when the electric charge on the passive network 109 surpasses appropriate threshold, apply with from (for example measuring relative " DELTA " electric charge of electric charge that electric capacity 102 shares, via the DELTA electric capacity 126 among Fig. 1), change electric charge (step 210) on the passive network 109 to use such as above-mentioned those conventional SIGMA-DELTA technology.In many examples, when electric charge did not surpass threshold value, the electric charge on the passive network 109 can also be changed (though be different from step 208 applied quantity) (step 211), although this feature is optional in all embodiments.Under the situation of a plurality of threshold values, can feed back different charge values.What note is, in the different conditions of recharge cycle step, the electric charge by each electric capacity (for example, can measure electric capacity, DELTA electric capacity, integrating capacitor) shifts and can change direction, shifts but refer to net charge here.By this way, if can measure electric capacity 102 in scope, then the associated voltage that can be held on the passive network 109 of the electric charge on the passive network 109 is approximately equal to threshold value (V _TH) needed electric charge.This is that because control loop, the voltage on the integrating capacitor 108 is approximate during operation to keep constant because the output of quantizer 110 is fed (instantaneous at this with reference to figure 1) via the DELTA electric capacity 126 in the clean degeneration factor.

[0039] in step 206, measure quantized (for example, numeral) numerical value and/or any amount that obtains therefrom are (for example, be included in " height " or " low " numerical value in the specific period) can easily be stored in the data that conduct has quantized in the storer, and then suitably by digital filtering or other processing (step 212).In conjunction with the SIGMA-DELTA measuring technique, successfully implement various wave filters, comprise conventional digital finite impulse response (FIR) wave filter, for example triangular filter, average filter and Kaiser wave filter also have infinite impulse response (IIR) wave filter.

[0040] can be individually and/or the concentrated area repeat arbitrarily time to apply voltage, electric charge transfer, charge variation and/or other step (step 214), to realize a plurality of useful features.For example, by obtaining to measure a plurality of quantized values of electric capacity 102, the numerical value that records can easily be extracted in control circuit, filtering, average and/or other digital processing, to reduce The noise, provides the measured value and/or the similar value of cumulative reliability.Many these features are described below.

[0041] many embodiment advantage is, only use passive element in conjunction with the conventional digitial controller such as microcontroller, digital signal processor, microprocessor, programmable logic array, special IC and/or analog, can easily realize general capacitive transducer.A large amount of these products are obtained from each commercial sources easily, comprise Microchip Technologies of Chandler, Arizona; FreescaleSemiconductor of Austin, Texas; With Texas Instruments Inc. (TI) of Dallas, Texas.Many control circuits described here comprise the number storage (for example, static, dynamic or flash memory random access memory) that can be used for storing data and instruction, and described data and instruction are used to carry out each SIGMA-DELTA handling procedure described here.For example, handle 200 executable instructions that can use a computer and easily be implemented, described computer executable instructions is carried out by one or more control circuit as described herein.

[0042] Fig. 3-8 illustrates several exemplary embodiments of the SIGMA-DELTA capacitive transducer that uses integral control circuit and realized by the simple passive network that capacitor and/or resistance are formed.Can in many ways any these embodiment be replenished or change, to produce the alternative embodiment of any amount.

[0043] with reference now to Fig. 3 A, typical capacitance sensor 300 suitably comprises controller 302, this controller has at least three input/output signal pins (I/O) 304,306 and 308 and the associated circuits that plays these signal pins of on-off action in controller 102, this switch transition is to power supply and ground (if perhaps suitable, being transformed into other reference value).In the example of Fig. 3 A, I/O ₃(pin 308) with can measure electric capacity 102 and be coupled, and all the other two pin I/O ₁(pin 304) and I/O ₂(pin 306) is coupled with passive network 109, and this passive network 109 comprises integrating capacitor 108, and this integrating capacitor is by measuring electric capacity 102 chargings and discharging by DELTA electric capacity 126, and perhaps vice versa.Integrating capacitor 108 usually selected with performance than the much bigger electric capacity of desired electric capacity that can measure electric capacity 102, and DELTA electric capacity 126 selected setting maximum detection amount electric capacity.Moreover concrete capacitance and relation can change according to specific embodiment, and the concrete structure of same signal pin and passive network 109 elements also can change.For example, Fig. 3 B shows " series connection " configuration of three pins, two capacitive transducers 350, and it is operated in the mode that is similar to the configuration that " walks abreast " shown in Fig. 3 A.

[0044] in each embodiment, by being controlled at the signal of placing and receiving on I/O (I/O) pin 304,306 and 308, the hardware in the controller 302, software and/or firmware logic suitably sort and control SIGMA-DELTA and measure processing.In exemplary operations, by measuring the voltage on the pin 308, controller 302 is sampled to the electric charge on the integrating capacitor 108 suitably.In other embodiments, can measure voltage on other node.Utilize ADC or schmidt trigger input on available numeral input threshold value, the plate in the control circuit 302, can quantize this voltage in many examples corresponding to the input of quantizer among Fig. 1 110.In other embodiments, can be provided for the voltage on the comparison pin 308 and the analog comparator circuit of suitable reference value 112 (Fig. 1).Although being used for the agreement of data representation can change with different embodiment, greater than the voltage on the integrating capacitor 108 of (pin 308) threshold value can with a logical value (for example, " 1 ") be associated, and can be associated with another logical value (for example, " 0 ") less than the voltage of threshold value.The data of these quantifications are used for aftertreatment by suitably storage (seeing top step 212).Notice that if having the input of hysteresis, for example the schmidt trigger input is used as quantizer 100, then shown in the method for

state

0,1 hysteresis is rested on the signal pin 308 with known state.

[0045] in Fig. 3 C-D, the typical technology that is used for application drawing 3A sensor circuit 300 is shown.In order to control the operation of passive network 109, the charging voltage of substantial constant is (for example, from battery, for example V _DDSupply voltage or other reference voltage) at first impose on the time span that can measure electric capacity 102 substantial constant, in Fig. 3 C-D, be shown as " state 1 ".Signal pin 306 also is driven to same charging voltage, remains on any electric charge on the DELTA electric capacity 126 with removal.Then, by high impedance in the middle of pin 306,308 is placed or " open circuit " state, can isolation impose on the electric charge that can measure electric capacity 102 on the electric capacity 102 can measuring, as shown in " state 2 ".This intermediateness is represented non-overlapped on off state, although there is not clear and definite released state also may realize this technology.Also available other insert high impedance status and handle other conversion.In state 3 by pin 304 is applied logic state voltage, share electric charge from measuring electric capacity 102 to passive network 109 subsequently, the opposite states of above-mentioned logic state and charging voltage (for example, by if charging voltage be " height ", then apply " low " state, vice versa).

[0046] in the above in the technology, when circuit 300 arrived steady state (SS)s, the voltage on the integrating capacitor 108 (with reference to pin 304) should keep general constant and approximate the threshold voltage of pin 308 (for example, the be associated V of I/O greatly _TH).Be driven to when low at signal pin 304, the voltage at signal pin 308 places keeps relatively the threshold value near input pin 308 similarly.Thereby when the output of sample quantization device in state 4, quantizer (signal pin 308) is output as the measured value of electric charge on the integrating capacitor 108.Depend on the sampling output (from the input that is associated of signal pin 308) of quantizer, the electric charge that state 5 changes on the integrating capacitor 108.If the sampling of quantizer (signal pin 308) output exceeds threshold value, then state 5A removes electric charge from integrating capacitor 108; Otherwise, do not have (perhaps negligible) electric charge to be removed (state 5B).After being set up (changing the electric charge on the integrating capacitor 108 of passive network 109) at the DELTA electric charge or skipping, signal pin 308 can be placed in high impedance status, with capture electric charge on the passive network 109 be used on pin 308 with post-sampling (state 6).When the data that quantized had been acquired and have stored, these data can be filtered suitably, extract or other are handled, to determine to measure the numerical value of electric capacity 102.Have in the situation of hysteresis at quantizer (for example signal pin 308), state 1 is set and is input as height, and the low threshold value that lags behind is like this determined output.

[0047] in alternative embodiment, integrating capacitor 108 is by measuring electric capacity 102 discharges and charging by DELTA electric capacity 126, and electric charge is changed when its landing is lower than quantizer threshold.In other modification, the plus or minus electric charge can be shared with integrating capacitor 108 with DELTA electric capacity 126 by measuring electric capacity 102, although there is not electric charge to be shared, also can use other node (for example, the pin 304 among Fig. 3 A) to be used for threshold measurement.

[0048] Fig. 4 A-B shows similar embodiment, and it allows only to realize the SIGMA-DELTA sampling with two signal pins on the controller 302 304,306.In Fig. 4 A embodiment 400, passive network 109 suitably comprises integrating capacitor 108, and it is connected with isolation resistance 402, this isolation resistance 402 with can measure electric capacity 102 and signal pin 306 is coupled.Fig. 4 A embodiment also comprises the DELTA electric capacity 126 that is coupled to signal pin 304,306.Fig. 4 A embodiment (and other) also selectively comprise and second electric capacity 407 between supply voltage and isolation resistance 402 suppress to increase power supply noise.Select second electric capacity 407, like this, be coupled to noise on the power supply of node 403 with identical with noise ratio on the power supply of the threshold value that is coupled to quantizer, this quantizer generally is expressed as 110 in Figure 1A.Also available other layouts reduce the influence of power supply noise, two examples shown in Fig. 9 A-B.Fig. 9 A shows resistance 901 in parallel with electric capacity 407A and that connect with electric capacity 407B, and described electric capacity 407B is coupled to one or more integrating capacitors 108.Fig. 9 B shows two resistance 903,905 that form voltage divider, and it is coupled to one or more integrating capacitors 108, and does not have discrete second electric capacity.The alternative that comprises the second electric capacity 407A, B or one of utilize in those shown in Fig. 9 A-B for example is particularly useful for the system with a plurality of integrating capacitors 108.Although only show an integrating capacitor 108 together with the second electric capacity 407A, B and alternative, a plurality of integrating capacitors can be shared same node." series connection " modification of 400 shows passive network 109 among Fig. 4 B, and it comprises making can measure the isolation resistance 402 that electric capacity 102 separates with integrating capacitor 108.

[0049] in these two embodiment, use charging pulse to charge to measuring electric capacity 102, described charging pulse is enough short in being blocked basically by the RC time constant, and described RC time constant produces by integrating capacitor 108 and isolation resistance 402.Equally, charging pulse preferably also is shorter than the RC time constant that can measure electric capacity and isolation resistance.This allow to use identical pin to compress into row and measure measuring electric capacity 102 and charge and integrating capacitor 108 being powered on.In two embodiment, the voltage that records on each signal pin 304 or pin 306 can determine whether share with integrating capacitor 108 from the electric charge of DELTA electric capacity 126.In the embodiment of Fig. 4 A, signal pin 306 is used to charging voltage imposed on can measure electric capacity 102, and signal pin 304 is used for charging voltage is imposed on DELTA electric capacity 126.The embodiment of Fig. 4 B is different, and signal pin 306 is used for charging voltage is imposed on DELTA electric capacity 126 changing the electric charge on the integrating capacitor 108, and signal pin 304 is used for charging voltage imposed on and can measures electric capacity 102.What note is, in the embodiment of Fig. 4 B, simply be if do not share electric charge from DELTA electric capacity 126, then share electric charge more than 108 time from measuring electric capacity 102 to integrating capacitor, if perhaps do not share electric charge, then share electric charge more than 108 time from DELTA electric capacity 126 to integrating capacitor from measuring electric capacity 102.

[0050] in many these embodiment, " current canceling " voltage can be prior to charging voltage.The timing of control " current canceling " voltage so that in state 0 " parasitism " quantity of electric charge by isolation resistance 402 removals be generally equal in state 1 by isolation resistance 402 and be added " parasitism " quantity of electric charge to integrating capacitor 108, and with can measure electric capacity 102 before passive network 109 is shared and be in correct charging voltage.This may allow in the passive network 109 than Low ESR, for example be used for the low numerical value of isolation resistance 402, and be used for the faster time constant of passive network 109 on the whole, can not measure the requirement of electric capacity charging sequential and change.

[0051] can measure electric capacity 102 and share electric charge by isolation resistance 402 with integrating capacitor 108.Because by the RC time delay that resistance produces, this embodiment more the time that is used to share electric charge than consuming with reference to figure 4 described three-prong embodiment more.Yet, be used to implement the number of the switch/logic pin of this sensor by minimizing, the additional detections passage can be arranged on the common chip, thereby allow to improve efficient among some embodiment.

[0052] typical circuit shown in Fig. 4 A-B can improve with many methods, to realize the other characteristics of any amount.Have among the embodiment of relative accurate timing at controller 302, for example, DELTA electric capacity 126 can be replaced by conventional resistance, and by simply pin 304 (pin 306 among Fig. 4 B) being encouraged the preset time section, " DELTA " electric charge can be imposed on integrating capacitor 108.In addition, to be present in any lagging influence in the ADC feature of signal pin 306 in minimizing can be useful to isolation resistance 402.

[0053] a kind of technology that is used for the circuit 400 shown in the application drawing 4A is displayed on the constitutional diagram of Fig. 4 C and the sequential chart of Fig. 4 D.With reference to these figure,, selectively begin measuring the processing that electric capacity 102 level detect by signal pin 306 being placed known (for example logic low) state (state 0).Because isolation resistance 402 produces the RC time constant with integrating capacitor 108, so section blink before at every turn reading circulation, pin 306 (pin 304 among Fig. 4 B) (for example can be placed in known state, logic low state), there is not obviously to influence the quantity of electric charge that is stored on the integrating capacitor 108.Before electric charge was sampled on to integrating capacitor 108, by signal pin 306 is placed known state even very short time, the hysteresis on the pin 306 was known, and can be compensated in controller 302.If the timing Be Controlled of

state

0,1 then can also make during these states and flow through the spurious charge that resistance 402 enters integrating capacitor 108 and minimize.

[0054] then, charge to measuring electric capacity 102, and by two pins 304,306 being placed known (height) logic state remove DELTA electric capacity 126, as shown in state 1.By making pin 306 become high impedance status (state 2), can measure trap-charge on the electric capacity subsequently, and then allow enough time delay subsequently, so that electric charge is shared (for example, charge or discharge) to integrating capacitor 108 by isolation resistance 402 from measuring electric capacity 102.From can measuring after electric capacity 102 shared, be applied in or be not applied in (in front in the state 6) based on the voltage that on integrating capacitor 108, records at electric charge from " DELTA " electric charge of DELTA electric capacity 126.In an illustrated embodiment, be used for determining that voltage level that whether " DELTA " electric charge be applied in before repeats acquisition from what SIGMA-DELTA handled.In other embodiments, can be only " DELTA electric charge " apply with share before or at other some place of testing process, can measuring voltage (for example, state 3).

[0055] uses the sensor 500 shown in Fig. 5, can realize further minimizing, wherein can measure electric capacity 102 and be coupled to the individual signals pin 306 of controller 302 by the passive network 109 that integrating capacitor 108 and isolation capacitance 402 are formed the signal pin purposes.Be similar to Fig. 4 A embodiment, Fig. 5 A embodiment can also selectively comprise second electric capacity 407 between supply voltage and isolation resistance 402, and one of circuit shown in perhaps replaceable for example Fig. 9 A-B suppresses to increase power supply noise.In this embodiment, can measure electric capacity 102 reuses potential pulse and charges, described potential pulse has the cycle less than the RC time constant that is produced by isolation resistance 402 and integrating capacitor 108, to reduce or to eliminate being stored in the adverse effect of electric charge on the integrating capacitor 108.Can measure electric capacity 102 by isolation capacitance 402 discharges, as mentioned above, and,, " DELTA " electric charge is applied to integrating capacitor 108 to continue the known time section by isolation resistance 402 drive currents by on pin 306, placing sparking voltage.Because sensor 500 comprises aforesaid isolation resistance 402,, can apply the compensation that lags behind on the pin 306 similarly by before sampling, this pin being placed known state.By the timing of control charging voltage and " electric current elimination " voltage, can also make the parasitic current minimum of during

state

0 and 1, passing through resistance 402.

[0056] is used to operate the typical technology of sort circuit shown in Fig. 5 B and the 5C.With reference to these figure, selectively set pin 306 before charging voltage so that " electric current elimination " voltage (for example, ground connection) to be provided; Select the length of " electric current elimination " voltage so that removed spurious charge amount mainly equals the spurious charge amount by the charging pulse interpolation.By with the after-applied potential pulse that has the short relatively duration (comparing), can allow then to share electric charge (state 2) to integrating capacitor 108 measuring electric capacity 102 chargings (state 1) by isolation resistance 402 with the RC time constant of network.After electric charge is shared the enough time in the past, can measure this electric charge (state 3) by the voltage on the pin 306 is sampled, and if suitably then " DELTA " electric charge can be applied (or not applying) to integrating capacitor 108 (state 4) based on the voltage of measuring.Moreover, in this embodiment, continue the suitable time by on signal pin 306, applying suitable voltage, apply " DELTA " electric charge simply, so that the variation that the charge generation on the integrating capacitor 108 is wanted.

[0057] above-described general structure, notion and technology can or be replenished with many distinct methods changes, and can use in the equivalent again embodiment of many differences.For example, two examples of the circuit of electric capacity on the technology for detection hyperchannel shown in above Fig. 6 A-B shows and can use.With reference now to Fig. 6 A,, show typical two channel position sensors 600, it has two detecting electrodes 602,604, and each detecting electrode is corresponding to the electric capacity of discussing in the above measured 102.When finger, contact pilotage or other object during near arbitrary electrode 602,604, the electric capacity of this node is existing related mode to change with object.Another kind of expression method is, by measuring the electric capacity of that electrode channel, can determine with arbitrary electrode 602,604 near to or in contact with the existence of object.

[0058] the employed detection scheme of each passage (A and B) at sensor 600 generally makes parallel about two pin sensors 400 described in Fig. 4 A in the above.Certainly, alternative embodiment may use any other technology of described here or reference.In the exemplary embodiments of Fig. 6 A, then, the pin 306,310 via controller 302 imposes on electrode 602,604 with voltage respectively.Allow each electrode 602,604 to share electric charge with integrating capacitor 108A, 108B by isolation resistance 402A, 402B (difference).And then, by quantizing the voltage at signal pin 306,310 places, the charge level that remains on each integrating capacitor 108A-B is sampled, by operation, apply arbitrarily essential " DELTA " electric charge from DELTA electric capacity 126A-B to change the electric charge on the correlation integral electric capacity to signal pin 304,308.

[0059] even further, the symmetry of sense channel makes embodiment can have common elements.For example, required any integrating capacitor, DELTA electric capacity and/or resistance can be shared between a plurality of sensor passages.An exemplary embodiments has been shown in Fig. 6 B.This use of common elements can obviously reduce the cost and the size of total system.In fact, can realize various technology, be used for wide array, any discrete component in signal pin on the shared control unit 302 and/or the passive network 109 at alternative embodiment.

[0060] by on common control unit 302, implementing many sense channels, can realize many efficient.Frequently, other electrodes that are used for measuring the detecting electrode of electric capacity and are used for DELTA electric capacity can easily be formed on standard printed circuit board (PCB), therefore in that to make duplicating of these elements on the meaning relatively cheap.Yet, some parts, for example integrating capacitor 108 and isolation resistance 402 can be enough greatly to ensure discrete component.Similarly, under the situation that relates to DELTA electric capacity degree of accuracy, it also can be used as discrete component and implements.In certain embodiments, use printing ink processing etc., can form one or more isolation resistances 402 on PCB, wherein electrically conductive ink has than the high impedance of employed typical material in PCB handles.This can be enough in many examples, because the actual value of isolation resistance 402 does not directly influence the degree of accuracy or the performance of this system usually.And in can measuring the relatively little situation of electric capacity 102, then integrating capacitor 108 can also can be made on PCB, for example by using polyimide flexible printed circuit etc.As a result, use conventional manufacturing technology and structure, can easily implement many various features recited above.In addition, by time, frequency, code or other multiplexing technique of any kind, even can further reduce total quantity of desired signal pin and the number of elements in the passive network 109.

[0061] allows to form many sensors of various types layouts (comprising the multidimensional layout of setting up with one dimension, bidimensional or multidimensional touch pad array) with the conventional arranged in patterns sensing electrode 602,604 of any amount.Replacedly, many " button " type touch sensor can easily be formed by various passages, perhaps can produce other sensor of any amount.

[0062] further, various SIGMA-DELTA detection techniques described herein in conjunction with hyperchannel is integrated easily, provide the efficient application of monitored signal.When the detection signal passage, multisensor passage 602,604 to the connection of common control unit 302 allows to apply monitored signal to mornitoring electrode 605.Generally speaking, wish to make each sensor electrode 602,604 and undesired electric signal isolation, comprise from other electrode with from external sensor 600,650 false other signals that receive.Have common reference and logic voltage because each passage in the sensor 600 can be implemented easily, can easily suppose: the time average of viewed common magnitude of voltage is roughly mutually the same on various sensor electrodes 602,604.By being applied to various electrodes from the monitored signal of low impedance source between craticular stage in addition, can reduce the quantity of false influence so.In fact, may to have a sensor electrode of similar detecting electrode voltage swing to all effective for single monitored signal.

[0063] the low-impedance voltage source plays a leading role to other coupled signal on the node, just as the low-impedance end comparison high impedance end of voltage divider (perhaps more generally impedance divider) accounts for leading.That is to say that for the set of voltage source, we can be similar to and regard single Thevenin impedance and the single Thevenin voltage of being dominated by the lowest impedance parts as, if this lowest impedance is basically less than the parallel impedance in all other sources.The purpose of example hereto, the impedance output of reference voltage, signal pin output, switch or I/O output will have enough low impedance at this node place, and other source is unconspicuous at the frequency range place that is considered.Similarly, have Low ESR when (for example, reference voltage etc.) when all the other far-ends of integrating capacitor are driven, the node that is coupled to the integrating capacitor nearside has sufficiently high electric capacity (and Low ESR), its leading other capacitive couplings source.That is, be driven when having low impedance source at far-end, this integrating capacitor can setting voltage and is absorbed most of electric charge from other higher resistance source at near-end.Obviously, the time cycle of being considered (or frequency) is also depended in the main impedance in the network.Therefore, on long-time scope (for example sharing), the impedance of connecting with integrating capacitor possibly can't change the state of integrating capacitor as accounting for leading Low ESR parts, and in short time range (for example, charging) on, because series impedance, the impedance of the electric capacity measured on this node may account for leading.By at correct node with correct speed energizing switch, can select leading low impedance element, and then suitably guide electric charge.

[0064] although monitoring technology is selectable and obviously changes with embodiment that a technology comprises to mornitoring electrode 605 and apply monitoring voltage that described monitoring voltage approximates the voltage that imposes on active electrode (for example, electrode 602 or 604) between charge period greatly.At electric charge to relevant integrating capacitor (for example from the active sensor electrode, be used for the electric capacity 108A of sensor 600 or 108B and be used for the electric capacity 108 of sensor 650) shift finish before (step 204 of Fig. 2), the voltage that imposes on mornitoring electrode 605 changes, and approximates voltage on active sensor electrode and the correlation integral electric capacity (active sensor electrode and correlation integral electric capacity are shared when occurring usually near same voltage at electric charge) greatly.Because the threshold voltage of quantizer is approximately equal to the voltage on the correlation integral electric capacity when the feedback loop Be Controlled, (for example can use the dependent quantization device, signal pin on the identity element, I/O) threshold voltage control monitoring voltage, as for example agency of voltage on the correlation integral electric capacity in the system shown in Fig. 6 B.Replacedly, when impedance divider output susceptibility is similar to the quantizer threshold susceptibility and becomes ratio with power supply, can use impedance divider reduction power changing sensitive degree; The example of this impedance divider illustrates by the voltage divider that is formed by resistance 606,608 among Fig. 6 A.In another embodiment, monitoring swing (with the electric charge that shifts from mornitoring electrode) may be repeated to another from of charge transfer process and repeat to change (charge transfer process comprise apply step, allow step and change step).This monitoring voltage swing may be on average to the identical voltage swing of voltage swing on detecting electrode.If the variation of monitoring swing has zero swing in some cases and has steady state value under the situation in addition, this makes the pulse code modulation (PCM) monitoring technology without any need for extra parts.Skew between mornitoring electrode voltage and the detecting electrode voltage can not influence the serviceability of this monitoring, because for the electric charge by electric capacity shifted, important only was change in voltage.

[0065] utilize the impedance divider that uses two

resistance

606 and 608 although should be noted in the discussion above that sensor 600, this only is an exemplary types of operable impedance divider.Particularly, common impedance divider comprises two passive impedances of series connection, and each passive impedance is coupled at least two nodes.One of these nodes are two common nodes that impedance was coupled.This common node provides the output of this impedance divider.This impedance divider is output as voltage and/or the electric current function in time that imposes on " not common points ".The simple case of impedance divider is a voltage divider, and it comprises two electric capacity or two resistance (for example resistance 606,608).Yet, can also use more complicated impedance divider.These more complicated impedance dividers can comprise unmatched electric capacity, resistance or the inductance of serial or parallel connection.In addition, single impedance can have capacitive character, resistive or inductive combination of features.

[0066] if suitable, can use the feature relevant to apply monitoring voltage with signal pin 604 (Fig. 6 A) or 310 (Fig. 6 B).In the embodiment of Fig. 6 A, for example, use

resistance

606 and 608 to constitute power supply (V _DD) voltage divider, in the voltage divider circuit or outside use pin 602 effectively transition resistance 608 produce two separation voltages that impose on mornitoring electrode 605.Embodiment shown in Fig. 6 B shows the allotter circuit that comprises resistance 608 and capacitor 614 similarly, and signal pin 310 control imposes on mornitoring electrode 605 with charging voltage or be discharged into the monitoring voltage (playing the effect of circuit 500 shown in Fig. 5 A when it shares electric charge more) of threshold voltage.For monitoring most effectively, the impedance that drives monitoring voltage should be less than the total sensors coupled impedance to mornitoring electrode.Can also use various other monitoring technologies, it comprises active analog element, for example the impact damper exclusive disjunction amplifier (OP-AMPS) of tracking transducer or reference channel.Although Fig. 6 A-B usually based in conjunction with the described embodiment of top Fig. 4 A-D, can be applied in the monitoring notion on the capacitive sensor of wide array.Yet, guard to not being based upon the optional feature on all embodiment.

[0067] many replacement detection schemes have used on discrete elements and/or the controller 102 logic pin sharing on a plurality of sense channels.For example, the sensor 650 shown in Fig. 6 B shows simple technique, thereby DELTA electric capacity 126 and integrating capacitor 108 are shared between two detecting electrodes 602,604.Sensor 700 shown in Fig. 7 A shows simple technique similarly, uses this simple technique, and the signal pin 308 of using DELTA electric capacity 126 can be shared between two sense channels (electric capacity 102A-B is represented by measuring).In this embodiment, sensor 700 is operated in conjunction with the mode of the described sensor 350 of Fig. 3 B to be similar in the above, but the DELTA electric capacity 126A-B side that provides by common signal pin 308 is provided electric charge.Usually, this embodiment changes phase place, to determine that whether concrete integrating capacitor (for example 108A or 108B) is to the transformation sensitivity on the corresponding DELTA electric capacity (126A and 126B).Particularly, according to which side that drives integrating capacitor with Low ESR, each integrating capacitor can selectively be shared electric charge or intercept from the electric charge transfer that can measure electric capacity or DELTA electric capacity.Therefore, can allow each DELTA electric capacity to change not influencing under the situation that to measure electric capacity, and then signal pin 308 can be shared with a plurality of sensors, reduce number of pins.For changing capacitor system, driven detecting electrode (for example 802 among Fig. 8 A) can also be shared with a plurality of sensors.These notions can be applied to the other sense channel of any amount similarly, measure re-using between the electric capacity 102 with further element and/or the signal pin of improving a plurality of.

[0068] Fig. 7 B comprises the constitutional diagram 750 of the typicalness sequence that sensor 700 is shown.Together with reference to figure 7A, 7B, first state 1 is to make and can measure capacitor discharge by pin 304 and 312 being set to 0, uses the voltage at I/O measurement (quantification) integrating capacitor place relevant with pin 306,310 simultaneously.At the example shown in the transformation of the constitutional diagram that is used for pin 304,306, the voltage that described transformation indication is measured at pin 306 places during state 1 be high (quantized data 1), and the voltage of transformation indication pin 310 measurements during state 1 that is used for the constitutional diagram of pin 310,312 is low (quantized data 0).According to they measured values separately, these different conditions change the different DELTA electric charges that cause among the state 5-8 to be shifted.It is also noted that the transformation of impedance from high to low may take place the state according to pin 304 and 312 fronts in the measurement of front and the state 8 in state 1.Because this transformation, any voltage swing at pin 306 and 310 places will cause from stray capacitance and DELTA electric capacity 126A-B to they separately some electric charge of integrating capacitor 108A-B share.This may cause in the skew of determining to measure in the electric capacity, but as long as it is little and constant, it just can be deducted, and then will be minimum to the influence of dynamic range.

High impedance status in the middle of [0069] second state 2 comprises.In this state, signal pin 304,306,310 and 312 is all temporarily remained on high impedance status, and it is low that pin 308 drives DELTA electric capacity 126A-B.This causes intermediateness, makes each capacitor uncoupling with temporary transient trap-charge in these capacitors.This guarantees not exist superposed signal, and it may not inadvertently be provided with undesired electric charge in addition on capacitor.

[0070] third state 3 makes the integrating capacitor 108A that is coupled to DELTA electric capacity 126A-B, the electrode of 108B be in logic high voltage.This causes that the voltage that can measure on the electric capacity 102A-B changes, and shares electric charge with their integrating capacitor 108A-B separately.Simultaneously, be Low ESR by signal pin 306,308 is driven, the electric charge transfer that is coupled by DELTA electric capacity 126A-B gets clogged.

[0071] because the both sides of these capacitors all are set to the identity logic high voltage by pin 306,308 and 310, the electric charge that four condition 4 is removed on DELTA electric capacity 126A and the 126B.

[0072] the 5th state 5 makes pin 306 be in high impedance status, and this remains on the integrating capacitor 108A electric charge.Before it changed in subsequent state 5, concerning can measuring electric capacity 102A, this was the middle high impedance status on the signal pin 304, and stoped electric charge not inadvertently to be arranged on the integrating capacitor 108A.What note is, the I/O that only is coupled to integrating capacitor 108A is by uncoupling, and described I/O has the voltage of quantized data measured value 1 at pin 306 places.The pin 310 that is coupled to integrating capacitor 108B keeps being driven to logic high voltage, and described integrating capacitor 108B has the voltage of quantized data measured value 0 at pin 310 places, and this is because integrating capacitor does not require the electric charge change by DELTA electric capacity 126B.

[0073] the 6th state 6 drive signal pins 304 are to low logic level, so that the DELTA electric charge can pass to integrating capacitor 108A by DELTA electric capacity 126A in later step 7.What note is that pin 310 keeps being urged to logic high, is blocked in and shifts this DELTA capacitance charge between 126B and the 108B.What also note is, the low logic level on this pin 304 changes and causes that also electric charge is in this step rather than share with DELTA electric capacity from stray capacitance in the next step 1 as has been described.

The voltage that [0074] the 7th state 7 changes on the pin 308, to remove electric charge by DELTA electric capacity 126A from integrating capacitor 108A, the electric charge on the integrating capacitor 108B is unaffected basically simultaneously.

[0075] final state 8 comprise be used for integrating capacitor (for example, 108B) second in the middle of high impedance status, it does not need the electric charge in the step 7 to change, and prepares them and be used for sharing of later step.This is each capacitor of uncoupling once more, with trap-charge in these capacitors temporarily.

[0076] after final state 8 was finished, this method turned back to step 1, and state 1-8 is carried out once more.Should be noted in the discussion above that this order is according to the measured value of the voltage on pin 306, the 308 integrating capacitor 108A-B of place be suitable for determining that the quantized data (for example, 0 or 1) that they can measure electric capacity 102A separately bears results.Be used for to measure electric capacity 102A and pin 304,306 and can measure electric capacity 102B and the sequence of steps of pin 310,312 only is the voltage on the pin 306,310 specifically to be measured the example of (and quantize) at exemplary step 1, according to the measurement in this duplicate measurements cycle, arbitrary sequence of states can appear can measuring on electric capacity and the integrating capacitor.Usually, in the measurement that can measure electric capacity, two states order will appear on the relevant pins, and two types the quantized data that obtains (for example 0 or 1) will become the part that is used for determining measuring any result of electric capacity.

[0077] should be noted in the discussion above that this embodiment has several advantages.For example, because public pole (that is, pin 308) is driven always, therefore can reduce the influence of stray capacitance significantly.Secondly, sensor 700 can reduce the round-robin quantity of using the IO state and a plurality of electric capacity being sampled and spent, and this is because it allows parallel sampling (that is, quantizing simultaneously) on a plurality of I/O.At last, many when measuring electric capacity when detecting, it allows the IO of obvious much less.This embodiment can also reduce the sensitivity to external noise during the integrating capacitor charge measurement, described external noise is by measuring electric capacity or other relevant stray capacitance coupling, described electric capacity or the stray capacitance measured can be measured electric capacity (that is, pin 304,312) node ground connection and be coupled to pin 304,312 by being coupled to.

[0078] although the embodiment shown in top generally emphasizes what is called " absolute capacitance " sensor, wherein can measure electric capacity about the local system earthmeter, similar concept can be applicable to the capacitive transducer of other type.For example, Fig. 8 A shows another embodiment of sensor 800, and it is designed to work with so-called " being driven electric capacity " or " conversion electric capacity " sensor.When integrating capacitor 108 and DELTA electric capacity 126 with can measure electric capacity 102 and connect the time, sensor 800 is " series connection " sensor.In the embodiment shown in Fig. 8 A, can measure electric capacity 102 and form by two separate mesh electrodes 802,804, the signal pin 304,306 of use controller 302 can be with each electrode drive to one voltage.When drive waveforms on " driving " electrode 802, use the capacitive couplings of SIGMA-DELTA detection technique recited above between can detecting electrode 802,804, the electric charge that detects between electrode 802,804 and shift to the passive network 109 that comprises integrating capacitor 108.The result is that under the situation that is not having obviously change, the sensor that depends on capacitively coupled change between " driving " and " detection " electrode can easily be realized above-mentioned notion.Note foregoingly, conversion can be measured other conductor and/or the dielectric influence that electric capacity can be subjected to any amount, so that produce complicated total effective capacitance near the parts of electrode 802,804.In addition, be similar to that to be used for DELTA electric capacity described and shown in the constitutional diagram 750, the phase deviation of during the repetition of charging cycle, sharing step can also be implemented block or allow with change capacitive transducer in " driving " electrode share electric charge.

[0079] Fig. 8 B comprises constitutional diagram 825, and it illustrates the typicalness order that is used for sensor 800.Together with reference to figure 8A and 8B, in first state 1, the state of the I/O4 by changing signal pin 310 by DELTA electric capacity 126 (Cd), can add the DELTA electric charge to integrating capacitor 108.In state 1, on 310 logic state from this change that is low to moderate high logic level (or just resting on lower) as F (V _CI) function, depend on that the front of the voltage on pin 308 place's integrating capacitors 108 in the state 7 in front quantizes.As an example, function F (V _CI), if in front in the circulation voltage ratio at integrating capacitor 108 places be used for the threshold voltage V of the I/O3 of signal pin 308 _THHigh (that is, electric charge is low on the integrating capacitor, and then voltage drop is less than expection), then pin 310 remains low.Otherwise, if the voltage ratio threshold voltage at integrating capacitor 108 places low (that is, electric charge is high on the integrating capacitor, and then voltage drop is greater than expection), then pin 310 is driven to height, to raise at 308 voltage by removing electric charges from integrating capacitor 108 by DELTA electric capacity 126.In at every turn the repeating of electric charge transfer processing, when I/O1 from lowly change height into, when integrating capacitor is added electric charge, electric charge is also by the capacitor C measured between electrode 802 and 804 _X102 shift.Under the control of SIGMA-DELTA system, add electric charge and remove electric charge by measuring electric capacity 102 by DELTA electric capacity 126, the electric charge on the integrating capacitor 108 keeps constant by negative feedback control is general.

[0080] thereby, the front voltage measurement based at the I/O3 place of pin 308 upper integral electric capacity utilizes DELTA electric capacity 126, state 1 is removed (being 1a) or is not removed (being 1b) electric charge from integrating capacitor 108.In alternative embodiment, this measurement may be implemented with the whole bag of tricks, and the voltage of for example measuring on the integrating capacitor can use pin 306.

[0081] state 2 is the middle high impedance status on the both sides (that is, signal pin 306,308) of integrating capacitor 108.This is the caputure integral electric charge on integrating capacitor 108, so that do not change thereon electric charge for any timing error in the output of signal pin.Pin 304 keeps driving to low, and pin 310 is retained in the state of its front.

[0082] in state 3, signal pin 308 is set to low logic state (for example, ground connection).What note is, measures the voltage on the pin 308 in front in the state 7, and should be near the input threshold value relevant with I/O3 with signal pin 308.By driving 308 to logic low state and change voltage on integrating capacitor 108 1 sides, the voltage at detecting electrode 804 places also changes, and integrating capacitor 108 with can measure electric capacity 102 and any other stray capacitance is shared electric charge, described stray capacitance is coupled to the electrode at signal pin 306 and sensor 804 places.In this typical case, and can measure electric charge that electric capacity 102 shares and be in equidirectional by the I/O1 that drives on the pin 304 for the high electric charge that shifts in the step below, although this needs not to be the situation in all embodiments.Although the meaning of this example is the function as the conversion capacitive transducer, but, because the change of arbitrary voltage on 804, share electric charge on the integrating capacitor 108 just as other " absolute capacitance " sensors, taking place that this paper other places are described from stray capacitance.This stray capacitance is shared on integrating capacitor 108, and in this example, will add electric charge to it, and minimizing pin 308 is in the measuring voltage on the integrating capacitor 108.

[0083] in four condition 4, when I/O1 on the pin 304 when logic low is changed into logic high voltage, share electric charge from electrode 804 to integrating capacitor 108, and then remove any electric charge on the DELTA electric capacity 126.Especially, in this state, pin 304 is driven to height, and pin 310 is low.This allows electric charge by measuring electric capacity 102 (C _X) share to integrating capacitor 108 from electrode 804.Simultaneously, at signal pin 310,308 places, the voltage on the both sides of DELTA electric capacity 126 is driven to low.Because the node at pin 308 places is in Low ESR, therefore in this step, there is not electric charge to transfer on the integrating capacitor 108 by DELTA electric capacity 126.

[0084] the 5th state 5 is another high impedance status of uncoupling integrating capacitor 108 both sides.

[0085] the 6th state 6 drives can measure electric capacity (C _X) 102 detecting electrode 804 is logic high voltage, share to block, and permission and DELTA electric capacity 126 are shared by the electric charge of detecting electrode 804 couplings.In next measuring process, on the signal pin 306 of I/O2, drive Low ESR, make integrating capacitor 108 shieldings be coupled to any noise of this electrode.It also allows electric charge by integrating capacitor 108 and the nodes sharing that is connected to signal pin 308 and DELTA electric capacity 126.Yet,, also change the voltage at signal pin node 308 places by on electrode 804, driving logic high voltage.This any stray capacitance and integrating capacitor 108 that causes that once more electric charge passes through on the pin 308 is shared.Though this needs not to be the situation among other embodiment,, in this example, be Low ESR because signal pin 310 is driven, electric charge is also shared with DELTA electric capacity 126.What note is, with can to measure sharing of electric capacity in the state 3 different, be driven to different voltages in the state 1 when changing the electric charge on the integrating capacitor at signal pin 310, this spurious charge will be in the reverse direction of the electric charge that shifts by DELTA electric capacity 126.Change with the voltage of stray capacitance and DELTA electric capacity and voltage on the integrating capacitor 108 will be shared and be tending towards increasing to the more proportional electric charges of size, and be reduced in the voltage of pin 308 places measurement.If pin 310 is in the anti-state of high impedance, this can be significantly reduced (reducing to only stray capacitance).Because it be high driving 306, if the voltage on 308 shift less than be used for deducting step 4 electric charge 310 on voltage shift, so, in conversion capacitive character SIGMA-DELTA processing, still can from net charge, deduct DELTA electric capacity 126.

The voltage that [0086] the 7th state 7 is measured on the integrating capacitor 108.When pin 308 was in high impedance status, with respect to the voltage that drives on detecting electrode by signal pin 306, (because integral charge) can measure the voltage on the integrating capacitor 108 at pin 308 places.This measurement can comprise the voltage at integrating capacitor 108 places and threshold voltage V _THCompare, so that the result of quantification to be provided.Then, during state 1-3, (that is, whether it is than threshold voltage V with voltage measurements on the integrating capacitor 108 _THHeight) is used for the F (V that round-robin repeats next time _CI) in, determine how the electric charge on the integrating capacitor may be changed by DELTA electric capacity 126.

[0087] therefore, will cause SIGMA-DELTA closed-loop control, and can use the filtering measured value of quantized result to come conversion electric capacity between

potential electrode

802 and 804 electric charge on the integrating capacitor 108 to repeating of state 1-7.The conversion electric capacity of this measurement can be further used for inspected object approaching or any other purpose with respect to sensor.

What [0088] note is, because stray capacitance, voltage at step 3 sharer node place of the integrating capacitor 108 relative with being driven node in 6 changes and causes that undesired electric charge shifts, and can cause by the electric charge that can measure electric capacity 102 or DELTA electric capacity 126 in the direction opposite with anticipated orientation and to share." absolute capacitance " behavior of this expression conversion capacitive sensor.These voltages change more little with respect to driving DELTA electric capacity 126 employed voltage swings by signal pin 304 drive electrodes 802 and signal pin 310, stray capacitance will have more little influence, and the function of conversion capacitive character SIGMA-DELTA measuring system is unreasonable thinks.

[0089] turns to Fig. 8 C and 8D now, show second embodiment of conversion capacitive sensor 850.Conversion capacitive sensor 850 be a line sensor also, promptly can measure in being connected of electric capacity 102 and integrating capacitor 108, and it is in parallel with DELTA electric capacity 126 to measure electric capacity 102.Also have, in this embodiment, near threshold voltage V _THVoltage V _GProduce by the voltage divider that comprises resistance 812 and 814.Embodiment is the same with the front, can measure electric capacity 102 and be formed by two

separate mesh electrodes

802 and 804, and each separate mesh electrode can utilize the signal pin 304,306 of controller 302 to be urged to a voltage.When drive waveforms on electrode 802, capacitive couplings between the electrode 802 and 804 (by measuring electric capacity 102 indication) can utilize the SIGMA-DELTA detection technique to detect, with the electric charge that detects between electrode 802,804 and shift to the passive network 109 that comprises integrating capacitor 108.

[0090] Fig. 8 D comprises the constitutional diagram 875 of the typicalness order that shows sensor 850.With reference to figure 8C and 8D, first state 1 comprises middle high impedance status together.In this state, signal pin 306,308A and 308B all are maintained at high impedance status, and pin 304 drives and is logic low-voltage, and pin 310 drivings are logic high voltage.This causes making the intermediateness of each capacitor uncoupling, with temporary transient trap-charge in these capacitors.This guarantees not exist superposed signal, and it may not inadvertently arrange unwanted electric charge in addition on capacitor.

[0091] in second state 2, the voltage V that the voltage on node 851 place's integrating capacitors 108 is set to generate _G, described V _GBe implemented and be substantially equal to measure I/O (for example, threshold voltage V IO3) _THParticularly, pin 308A provides logic high voltage (for example, V _DD), pin 308B provides logic low-voltage, and (for example, GND), and resistance 812 and 814 provides voltage divider, and this voltage divider produces voltage V at node 851 places _GIn an exemplary embodiments, resistance 812 and 814 equates that basically therefore, with CMOS input threshold, the voltage that is produced is similar to 1/2V _DDExist many methods to be used to use passive element and switch (for example, I/O or DAC) to apply the voltage that is produced, and this only is an example.The threshold voltage of numeral input is the voltage that low and high input is distinguished.Certainly, this only is an example, and in other embodiments, hope can utilize other numerical value.For example, utilize in the situation of Schmidt trigger input V at I/O _Dd/ 3 voltage may be similar to the input threshold value of I/O3, and described input threshold value only is set at logic high.Should also be noted that and do not use voltage divider in certain embodiments.Replace it, in certain embodiments, controller 302 comprises that inherently generation is near V _THSuitable voltage V _GAbility.

[0092] should also be noted that to have near threshold voltage V _THThe drive node 851 of the voltage Vg that is produced in step 2-3, reduce voltage swing on the electrode 804, reason is the electric charge on the SIGMA-DELTA feedback loop control integrating capacitor 108, keeping when signal pin 306 drive node 804 (in

step

5,6,7) voltage on the node 851, and can measure the input that is connected to node 851 (for example 308A) near threshold voltage.Owing to minimized the electric charge that does not move through stray capacitance, be that fixed voltage (for example, GND) does not have much relations so keep 804 and 851 place's voltage constants to make stray capacitance to a great extent.What note is, if be to implement with the I/O2 on the pin 306 to the measurement of the voltage on the integrating capacitor 108, then node 306 may use similar formation voltage Vg to drive influence with minimum parasitic capacitance.

[0093] in the third state 3, according to the front the 308A place to integrating capacitor 108 on the measurement of voltage, the DELTA electric charge is transferred to integrating capacitor 108 and/or electric charge is shared between electrode 804 and integrating capacitor 108.Particularly, to drive pin 310 be the front the 308A place to integrating capacitor 108 on the function F (V of voltage of measurement _CI).As an example, choice function F (V _CI), if so that the voltage of integrating capacitor 108 (for example at node 851 places) is higher than the threshold voltage V of front I/O3 in measuring the round-robin repetition _TH(that is, the electric charge on the integrating capacitor is low, and voltage drop is littler than what wish), then pin 310 remains on logic high voltage.Otherwise,, then drive pin 310 to logic low-voltage, to remove electric charge from integrating capacitor 108 by DELTA electric capacity 126 if the voltage at integrating capacitor 108 places is lower than threshold voltage (that is, the electric charge of integrating capacitor is high, and voltage drop is bigger than what wish).In all situations, when I/O1 from logic low-voltage change logic high voltage into, when adding electric charge to integrating capacitor, electric charge is also by the capacitor C measured between electrode 802 and 804 _X102 shift.Under the control of SIGMA-DELTA system, add electric charge and remove electric charge by measuring electric capacity by DELTA electric capacity, the electric charge on the integrating capacitor is probably kept constant by negative feedback control.

[0094] thereby, based on the front at the I/O3 place to the voltage measurement on the pin 308A of integrating capacitor, state 3 is shared electric charge between electrode 804 and integrating capacitor 108, perhaps utilize DELTA electric capacity 126 to remove electric charges from integrating capacitor 108.

[0095] four condition 4 comprises another middle high impedance status, and it guarantees not have in addition the signal of not wanting electric charge to be set on capacitor not inadvertently.The 5th state 5 by the I/O2 on the signal pin 306, is set to logic high voltage with receiving electrode 804 once more.The 6th state 6 is provided with can measure electric capacity (C _X) 102 and DELTA electric capacity (C _D) electric charge on 126, the transformation in repeating with next that prepare charge transfer process.Particularly, on pin 310, arrange logic high voltage, and arrange that on pin 306 logic high voltage makes 126 discharges of DELTA electric capacity.Simultaneously, on electrode 802, arrange logic low-voltage, the electric capacity measured that is coupled to electrode 804 is recharged by signal pin 304.By on the electrode in can measuring electric capacity 102 804 and in a side of the integrating capacitor 108 that is coupled to DELTA electric capacity 126 low-impedance voltage being set, electric charge shifts on integrating capacitor 108 can maybe can not measuring electric capacity 102 by DELTA electric capacity 126 during this step.This numerical value of guaranteeing integrating capacitor 108 keeps accurate transfer charge to represent during the step in front, and just can measure it under the situation of the noise that is not subjected to detecting electrode 804.

[0096] the 7th state 7 is measured the voltage at integrating capacitor 108 places.When pin 308 was in high impedance status, (because charges accumulated) can measure voltage on the integrating capacitor 108 voltage of node 851 places (for example) on pin 308A or the pin 308B.This measurement can comprise the voltage and the threshold voltage V at integrating capacitor 108 places _THComparison, so that quantized result to be provided.Then, during state 3-5, the measurement result of voltage on the integrating capacitor 108 is used for next round-robin F (V _CI) in (that is, whether it is higher than threshold voltage V _TH), determine how the electric charge on the integrating capacitor can change by DELTA electric capacity 126.

[0097] therefore, will cause SIGMA-DELTA closed-loop control, and the filtering measurement of quantized result be can be used for conversion electric capacity between

potential electrode

802 and 804 electric charge on the integrating capacitor 108 to repeating of state 1-7.The conversion electric capacity of this measurement can be further used for inspected object approaching with respect to sensor.

[0098] as mentioned above, sensor examples measure shown in Figure 8 is changed electric capacity rather than absolute or ground connection reference capacitance.These embodiment reduce the negative effect to the electric capacity measured of background or stray capacitance, thereby the application of the parasitic trace electric capacity that has higher proportion is particularly useful, and for example fingerprint line (fingerprintridge) detects and the capacitive touch detection.

[0099] for example, when on node 851, driving the voltage V that is produced _gWhen probably equaling to be coupled the input threshold voltage of signal pin of 851 (for example, wherein they are the 308A/B of I/O), the voltage swing quantity on institute's detecting electrode 804 can be remained low relatively level by the SIGMA-DELTA FEEDBACK CONTROL.This can reduce the sensitivity to stray capacitance fully.Just, owing to keep relatively near threshold voltage at the voltage on node 851 place's integrating capacitors 108 during the steady state operation, when driving voltage on node 851 (with 306 floating), and on 306 during driving voltage, by signal pin 308A/B drive node 851.Similarly, be similar to when with the result (rather than drive signal pin 306 to some other voltage) of node 851 place's driven when one of 308A/B locates to import threshold voltage because signal pin 306 is driven to, the voltage swing on the maintenance electrode 804 is for low relatively.Determine voltage difference between 851 and 306 by passing voltage (and electric charge) on the integrating capacitor, the voltage on the described integrating capacitor (and electric charge) is by the control of SIGMA-DELTA feedback loop.Can apply by any way 306 and node 851 on these voltages.In various embodiments, apply approximate threshold voltage,, thereby produce suitable voltage with the part of excitation or de-energisation divider network by the logic of utilizing pin 308A-B.Replacedly, can apply approximate voltage by digital to analog converter or by any other technology.

[00100] even, to shown various circuit and technology can be implemented more improvement and change here.Can use the above-mentioned technology that has or do not have extra active analog element, implement higher-order SIGMA-DELTA modulator.

[00101] in addition, for example, can reduce various noise sources by using the noise dither technology.Particularly, known conventional single order SIGMA-DELTA converter especially is vulnerable to the influence of noise " tone " (that is repetitive noise form).These tones can produce the noise output that is used for certain constant input (like this, having " dead band " under the situation of capacitive character sensitivity low (or replacedly, high level error)), cause the reduction to the response of initial conditions varied slightly.More complicated by utilizing (that is, more high-order) SIGMA-DELTA technology perhaps replacedly by the low power noise of smallest number is injected the SIGMA-DELTA converter, can be avoided tone.A kind of technology that is used to inject noise comprises noise dither is applied to ADC reference voltage (for example, the voltage among Fig. 1 112).This shake of generation in software or other logic can planted arbitrarily, and this shake is applied to each sense channel simultaneously to improve response.

[00102] as mentioned above, be used for determining that the equipment and the method for electric capacity specifically can be applicable to approaching sensor equipment.Now turn to Figure 10, block diagram shows the exemplary electronic system 10 that is coupled to approaching sensor equipment 11.Electronic system 10 is used to represent personal computer, portable computer, workstation, personal digital assistant, video game machine, communication facilities (comprising wireless telephone and information transfer apparatus), the media device of any type, and this media device comprises that logging machine and player (comprising TV, cable box, music player and video player) maybe can accept to import or the miscellaneous equipment of process information from the user.Therefore, each embodiment of system 10 can comprise processor, storer or the display of any type.In addition, the element of system 10 can be via bus, network or other wired or wireless interconnected communicating.By comprising any type of interface or the connection of I2C, SPI, PS/2, USB (universal serial bus) (USB), bluetooth, RF, IRDA, or the wired or wireless connection of other type arbitrarily, approaching sensor equipment 11 can be connected to system 10, has enumerated several non-limitative examples at this.

[00103] approaching sensor equipment 11 comprises controller 19 and surveyed area 18.11 pairs of approaching sensor equipment are imported the position sensing of 14 (they can be provided by one or more fingers, contact pilotage and/or other input object) in surveyed area 18, and can be by measuring because the input 14 electric capacity results change that cause detect input 14." surveyed area " 18 as used herein be included in widely approaching sensor equipment 11 top, on every side, the inside and/or near any space of approaching sensor equipment 11, the wherein position that sensor can inspected object.In conventional embodiment, surveyed area 18 launches a distance from sensor surface and enters the space one or more directions, stoped input to detect until signal to noise ratio (S/N ratio).This distance can be on less than millimeter, several millimeter, several centimetres or more quantity rank, and can change significantly with desired sensor electrode size, sensor design and/or sensor performance (for example, degree of accuracy or resolution).Therefore, the flatness in particular detection zone 18 or curvature, size, shape and exact position will change significantly with the different of embodiment.

[00104] in operation, by measuring and the relevant electric capacity measured of a plurality of detecting electrodes, approaching sensor equipment 11 suitably detects imports 14 position, the influence of its examined regional 18 interior one or more fingers, contact pilotage and/or other object.And, using controller 19, approaching sensor equipment 11 offers electronic system 10 with indication electricity or electronics of position.As discussed previously, this system 10 suitably handles this indication accepting from user's input being used for any appropriate purpose, and produces the response of any appropriate.

[00105] approaching sensor equipment 11 can use any other of discritized array or capacitive sensor electrode to arrange to support the surveyed area 18 of any amount.Approaching sensor equipment also can change the information type that is provided, (for example for example provide as " one dimension " positional information of scalar, along surveyed area), as " two dimension " positional information of combinations of values (for example, cross over two dimension horizontal/vertical, angle/radially or other axle arbitrarily), as approaching " two dimension " image of array of values etc.

[00106] utilize above-described various technology, the controller 19 that is called as approaching sensor processor or touch sensor controller is sometimes indicated the processing that is used to measure electric capacity usually.Here, controller 19 is also communicated by letter with electronic system 10.Controller 19 can be carried out various other processing, to realize approaching sensor equipment 11.For example, the single electric capacity of measuring can be selected or connect to controller 19, based on numerical evaluation position or the movable information that can measure electric capacity, position or the motion of report when reaching threshold value, and it is being reported to electronic system 10 or its indication is effectively clapped/struck to explaining before the user with wait/carve/fastening/order of making a sign with the hand or a plurality of different processing arbitrarily.

[00107] in this instructions, term " controller " is defined and comprises the one or more processing element that are suitable for carrying out described operation.Thereby controller 19 can comprise all or part of one or more integrated circuit, firmware code and/or software code.

[00108] moreover, the term that uses in using as this, term " electronic system " refers to the equipment of any type widely, it is communicated by letter with approaching sensor equipment 11.Therefore, electronic system 10 can comprise equipment or a plurality of equipment of any type, wherein can realize or coupled with touch sensors equipment.Use any suitable technique, this approaching sensor equipment 11 can be embodied as the part of electronic system 10 or be coupled to electronic system 10.Therefore, as non-limitative example, electronic system 10 can comprise any type computing equipment, media player, communication facilities or another input equipment (for example, other touch sensor equipment or keyboard).In some cases, electronic system 10 itself is the peripherals of big system.For example, electronic system 10 can be that data input or output equipment, for example remote control or display device (for example, remote-controlled television set), and it utilizes suitable wired or wireless technology and computing machine or media system to communicate.Should also be noted that each parts (processor, storer etc.) in the electronic system 10 can implement as the part in the total system, as the part in the touch sensor equipment or as its combination.In addition, electronic system 10 can be the master or the slave of approaching sensor equipment 11.

[00109] should also be noted that term " approaching sensor equipment " not only comprises conventional approaching sensor equipment, but also comprise a large amount of equal equipment of the position that can detect one or more fingers, contact pilotage and/or other object.This equipment can include, without being limited to touch-screen, touch dish, touch pad, biometrics evaluation apparatus, calligraphy or Character Font Recognition equipment or the like.Similarly, term as used herein " position " or " object space " comprise absolute and relative positional information widely, also comprise the spatial-domain information of other type, and for example speed, acceleration or the like are included in the motion measurement in one or more directions.Various forms of positional informations also can comprise the time history part, as in the situation of gesture identification etc.Therefore, approaching sensor equipment can suitable detection exist than object or the disappearance more information, and can comprise a large amount of equivalents.

[00110] it is also understood that mechanism of the present invention can distribute as various forms of program products.For example, the approaching sensor program that the readable computer signal supports medium (signal bearing media) can be implemented and be distributed as to mechanism of the present invention.Additionally, use embodiments of the invention equally, and support media-independent with the signal of the particular type that is used to carry out this distribution.The example that signal supports medium comprises: but the transmission medium of the recording medium of storage card, CD and disk, hard drives and for example numeral and analog communication links for example.

[00111] under the situation that does not break away from basic instruction, various other changes and improvements can be based on structure of illustrating here and technology implementation.Therefore, be provided for detecting and/or quantizing to measure numerous systems, equipment and the method for electric capacity.Although stated at least one example embodiment in the detailed in front instructions, should be understood that to have a large amount of modification.For example, each step of technology described here can be implemented with temporary transient order, is not limited to the order of stating and/or stating here.It is to be further understood that exemplary embodiments described here only is an example, be used to never in any form limit the scope of the invention, application or structure.Therefore, under situation about not breaking away from, can and arrange in functions of components and make various changes as the scope of the present invention in appended claims and legal equivalents thereof, set forth.

Claims (according to the modification of the 19th of treaty)

1. one kind is used to measure the method that can measure electric capacity, and the method comprising the steps of:

Use first switch that voltage is applied to and to measure electric capacity;

Permission can be measured electric capacity and be shared electric charge with passive network;

If the electric charge on the passive network surpasses threshold value, then the electric charge on the passive network is changed the electric charge of quantized amount; With

Repeating each applies step, allows step and changes step at least once.

2. according to the process of claim 1 wherein that described voltage is predetermined voltage, and the electric charge of quantized amount based on predetermined voltage.

3. according to the method for claim 1, further comprise, determine to measure the step of capacitance to small part based on the multiplicity that changes step.

4. according to the process of claim 1 wherein that the multiplicity that applies step is not equal to the multiplicity that changes step.

5. according to the process of claim 1 wherein that the change step comprises repeatedly the electric charge on the conversion passive network.

6. apply each time repetition that step is used to change step according to the process of claim 1 wherein repeatedly to carry out, and repeatedly carry out each time repetition that allows step to be used to change step.

7. according to the process of claim 1 wherein that applying step comprises the output pin that encourages digital control circuit.

8. according to the process of claim 1 wherein that electric charge in the quantized amount that changes on the passive network is corresponding to the electric charge on the feedback capacity.

9. according to the process of claim 1 wherein that the electric charge of the quantized amount that changes is corresponding to the electric current of the known a period of time that applies by resistance on passive network.

10. according to the method for claim 9, wherein apply electric current by applying second voltage at the resistance two ends.

11. according to the method for claim 1, further comprise the steps: multiplexedly between the electric capacity to apply step, allow step and change step a plurality of the measurement, wherein can measure electric capacity is a plurality of one of electric capacity of measuring.

12. according to the process of claim 1 wherein that only using switch and passive element to carry out applies and allow step.

13. according to the method for claim 12, wherein switch comprises the numeral output of controller.

14. apply, allow and change step according to the process of claim 1 wherein that the digital input and output of using controller are carried out.

15. according to the process of claim 1 wherein that the threshold voltage of the numeral input by controller determines threshold value.

16. determine threshold value by analog-to-digital converter according to the process of claim 1 wherein.

17. according to the process of claim 1 wherein that applying step comprises and charging to measuring electric capacity, and change step and comprise from passive network and remove electric charge.

18. according to the process of claim 1 wherein that applying step comprises and discharging to measuring electric capacity, and change step and comprise to passive network and add electric charge.

19. allow step to comprise that passive permission can measure electric capacity and use sharing circuit to share electric charge with passive network according to the process of claim 1 wherein, and apply step and take place soon than the time constant of sharing circuit basically.

20. allow step to comprise the control second switch according to the process of claim 1 wherein.

21., further comprise step according to the method for claim 1:

A plurality of charge values that quantized on the passive network are stored in the storer; With

To the filtering of a plurality of value Applied Digital.

22., further comprise monitoring voltage is applied to the step that is different from the mornitoring electrode that can measure electric capacity according to the method for claim 1.

23. according to the method for claim 22, the monitoring voltage that wherein imposes on mornitoring electrode during applying step is substantially equal to impose on the voltage that can measure electric capacity during applying step.

24. according to the method for claim 22, the monitoring voltage that wherein imposes on mornitoring electrode is substantially equal to can measure the voltage on the electric capacity after allowing step.

25. according to the method for claim 22, wherein in the approaching variation that is applying and allowing to measure between the step voltage on the electric capacity of the variation of the monitoring voltage that applies and allow to impose between the step mornitoring electrode.

26. a digital storage media, its have storage thereon, be configured to the computer executable instructions that enforcement of rights requires 1 method.

27. one kind is used to measure the system that can measure electric capacity, this system comprises:

Be used to use first switch that voltage is repeated to impose on the device that can measure electric capacity;

Be used to repeat to allow to measure electric capacity is shared electric charge with passive network device; With

If the electric charge that is used on the passive network surpasses threshold value, the loading that then passive network powered on changes the device of the electric charge of quantized amount again.

28. one kind is used to measure the circuit that can measure electric capacity, this circuit comprises:

First switch, it is coupled to can measure electric capacity;

Passive network, it is coupled to can measure electric capacity, and wherein passive network is configured to store from measuring the electric charge that electric capacity receives; With

The charge variation circuit, it is coupled to passive network; With

Controller, it is configured to by using first switch to repeat to apply voltage to measuring electric capacity, will be from the electric charge repeated storage that the electric capacity measured on the passive network received, and response surpasses electric charge on the passive network of threshold level, utilizes the charge variation circuit that the electric charge on the passive network is repeatedly changed the electric charge of quantized amount, thereby determines to measure the numerical value of electric capacity.

29. according to the circuit of claim 28, wherein said voltage is predetermined voltage, and the electric charge of quantized amount based on predetermined voltage.

30. according to the circuit of claim 28, wherein said voltage is supply voltage.

31. according to the circuit of claim 28, wherein passive network comprises capacitor.

32. according to the circuit of claim 28, wherein first switch is the numeral output of controller.

33. according to the circuit of claim 32, further comprise second switch, described second switch is coupled to electric charge and changes circuit and passive network, wherein second switch operationally changes the electric charge on the passive network electric charge of quantized amount.

34. according to the circuit of claim 32, further comprise the 3rd switch, described the 3rd switch is coupled to can measure electric capacity and passive network, wherein the 3rd switch operationally allows to measure electric capacity and shares electric charge with passive network.

35. according to the circuit of claim 28, further comprise second switch, described second switch is coupled to can measure electric capacity and passive network, wherein second switch operationally allows to measure electric capacity and shares electric charge with passive network.

36. according to the circuit of claim 31, wherein passive network comprises resistance.

37., further comprise the tension measuring circuit that is coupled to passive network according to the circuit of claim 28.

38. according to the circuit of claim 37, wherein tension measuring circuit comprises comparer.

39. according to the circuit of claim 37, wherein tension measuring circuit comprises analog-to-digital converter.

40. according to the circuit of claim 37, wherein tension measuring circuit comprises the input threshold value of the numeral input of controller.

41., wherein import threshold value and have hysteresis according to the circuit of claim 40.

42. according to the circuit of claim 28, further comprise the signal pin of controller, this signal pin is coupled to can measure electric capacity, its middle controller is configured to via this signal pin voltage be imposed on can measure electric capacity.

43. according to the circuit of claim 28, further comprise second switch and the 3rd switch, wherein passive network comprises:

First capacitor, it is coupling in the 3rd switch and can measures between the electric capacity; With

Second capacitor, it is coupling between first switch and the second switch.

44. according to the circuit of claim 28, further comprise second switch, wherein passive network comprises:

Be coupling in first capacitor between first switch and the second switch; With

Be coupled to first switch and the resistance that is coupled to second voltage; With

Be coupled to the resistance of second voltage.

45. according to the circuit of claim 28, wherein passive network comprises and is coupled in series to first switch mutually and capacitor and resistance that be coupled to second voltage.

46. according to the circuit of claim 28, further comprise second switch and the 3rd switch, wherein passive network comprises:

Be coupling in the 3rd switch and can measure capacitor between the electric capacity; With

Be coupling in the resistance between first switch and the second switch.

47., further be configured to change electric charge on the passive network, thereby allow the electric charge on the passive network to pass through resistance by excitation second switch certain hour section according to the circuit of claim 46.

48. according to the circuit of claim 28, further comprise mornitoring electrode, its middle controller further is configured to monitoring voltage is imposed on mornitoring electrode.

49. according to the circuit of claim 48, further comprise the impedance divider, it is coupled to second switch and mornitoring electrode.

50. the circuit according to claim 48 wherein drives mornitoring electrode by digital to analog converter.

Claims

Use first switch that voltage is applied to and to measure electric capacity;

If the electric charge on the passive network surpasses threshold value, then the electric charge on the passive network is changed the electric charge of some; With

Repeating each applies step, allows step and changes step at least once.

2. according to the process of claim 1 wherein that described voltage is predetermined voltage, and the electric charge of described quantity is based on predetermined voltage.

8. according to the process of claim 1 wherein in the amount of charge that changes on the passive network corresponding to the electric charge on the feedback capacity.

9. according to the process of claim 1 wherein the amount of charge that on passive network, changes electric current corresponding to the known a period of time that applies by resistance.

21., further comprise step according to the method for claim 1:

To the filtering of a plurality of value Applied Digital.

If the electric charge that is used on the passive network surpasses threshold value, the loading that then passive network powered on changes the device of some electric charges again.

First switch, it is coupled to can measure electric capacity;

The charge variation circuit, it is coupled to passive network; With

Controller, it is configured to by using first switch to repeat to apply voltage to measuring electric capacity, will be from the electric charge repeated storage that the electric capacity measured on the passive network received, and response surpasses electric charge on the passive network of threshold level, utilizes the charge variation circuit that the electric charge on the passive network is repeatedly changed the electric charge of some, thereby determines to measure the numerical value of electric capacity.

29. according to the circuit of claim 28, wherein said voltage is predetermined voltage, and amount of charge is based on predetermined voltage.

33. according to the circuit of claim 32, further comprise second switch, described second switch is coupled to electric charge and changes circuit and passive network, wherein second switch operationally changes the electric charge on the passive network electric charge of some.

Second capacitor, it is coupling between first switch and the second switch.

Be coupling in first capacitor between first switch and the second switch; With

Be coupled to the resistance of second voltage.

Be coupling in the resistance between first switch and the second switch.