CN111399704B - Capacitance detection circuit, touch chip and electronic equipment - Google Patents

Capacitance detection circuit, touch chip and electronic equipment Download PDF

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CN111399704B
CN111399704B CN202010487566.7A CN202010487566A CN111399704B CN 111399704 B CN111399704 B CN 111399704B CN 202010487566 A CN202010487566 A CN 202010487566A CN 111399704 B CN111399704 B CN 111399704B
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circuit
capacitance
current
ratio
output
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CN111399704A (en
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余倩
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Shenzhen Goodix Technology Co Ltd
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Shenzhen Goodix Technology Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0416—Control or interface arrangements specially adapted for digitisers
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/044—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means by capacitive means

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Human Computer Interaction (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Resistance Or Impedance (AREA)

Abstract

The application provides a capacitance detection circuit, a touch chip and an electronic device, which can effectively extract capacitance variation and do not increase circuit cost. The capacitance detection circuit includes: the CCA circuit comprises a first input end and a second input end which are respectively connected with a capacitor to be tested and a cancellation capacitor, a third input end of the CCA circuit is connected with a code printing voltage, a first output end and a second output end of the CCA circuit respectively output a first current and a second current, and the cancellation capacitor is smaller than an initial value of the capacitor to be tested; two input ends of the PGA circuit are respectively connected with two output ends of the CCA circuit; wherein a ratio between the first current and the second current is set to be equal to a ratio between an initial value of the capacitance to be measured and a cancellation capacitance, so that an output of the PGA circuit is 0 when the capacitance to be measured is the initial value, and the output of the PGA circuit is associated with a capacitance variation amount of the capacitance to be measured when the capacitance to be measured varies with respect to the initial value.

Description

Capacitance detection circuit, touch chip and electronic equipment
Technical Field
The embodiment of the application relates to the field of capacitance detection, and more particularly to a capacitance detection circuit, a touch chip and an electronic device.
Background
Capacitive sensors are widely used in electronic products to implement touch detection. In the capacitive sensor, a capacitance value is changed by a touch of a user's finger. The change of the capacitor can be read through the capacitor detection circuit, so that the operation of a user is judged based on the change of the capacitor, and better human-computer interaction experience is achieved. With the increase of the size of the touch screen and the update of the screen body technology, the capacitance value of the touch screen is also increasing, and how to effectively extract the tiny capacitance variation without increasing the cost of the capacitance detection circuit becomes a problem to be solved urgently.
Disclosure of Invention
The embodiment of the application provides a capacitance detection circuit, a touch chip and an electronic device, which can effectively extract a small capacitance variation and do not increase the cost of the capacitance detection circuit.
In a first aspect, a capacitance detection circuit is provided, which includes:
a first input end and a second input end of the CCA circuit are respectively connected with a capacitor to be tested and a cancellation capacitor, a third input end of the CCA circuit is connected with a code printing voltage, a first output end and a second output end of the CCA circuit respectively output a first current and a second current, and the cancellation capacitor is smaller than an initial value of the capacitor to be tested;
two input ends of the PGA circuit are respectively connected with the first output end and the second output end of the CCA circuit;
wherein a ratio between the first current and the second current is set equal to a ratio between an initial value of the capacitance to be measured and the offset capacitance, so that an output of the PGA circuit is 0 when the capacitance to be measured is the initial value, and the output of the PGA circuit is associated with a capacitance variation amount of the capacitance to be measured when the capacitance to be measured is varied with respect to the initial value.
In one possible implementation, the output stage of the CCA circuit includes a first circuit unit and a second circuit unit. The first circuit unit comprises a first P-channel Metal oxide semiconductor (PMOS) tube and a first N-channel Metal oxide semiconductor (PMOS) tube, and a drain electrode of the first PMOS tube, a drain electrode of the first NMOS tube and the first output end of the CCA circuit are connected. The second circuit unit comprises a second PMOS tube and a second NMOS tube, and the drain electrode of the second PMOS tube, the drain electrode of the second NMOS tube and the second output end of the CCA circuit are connected. The grid voltages of the first PMOS tube and the second PMOS tube are the same, and the grid voltages of the first NMOS tube and the second NMOS tube are the same.
In a possible implementation manner, the ratio between the first current and the second current is obtained by setting the ratio between the width-to-length ratio of the first PMOS transistor and the first NMOS transistor and the ratio between the width-to-length ratio of the second PMOS transistor and the second NMOS transistor.
In one possible implementation, the ratio between the first current and the second current is obtained by setting a ratio between the number of the first circuit units and the number of the second circuit units included in the CCA circuit.
In a possible implementation manner, a ratio between the first current and the second current output by the CCA circuit is adjustable, and the cancellation capacitor is an adjustable capacitor, wherein the output of the PGA circuit is 0 when the capacitor to be measured is the initial value by adjusting the ratio between the first current and the second current and/or the cancellation capacitor.
In one possible implementation, the ratio between the first current and the second current is between 5: 1 to 10: 1.
In one possible implementation, the PGA circuit includes a differential amplifier, and a feedback capacitor and a feedback resistor connected across an input terminal and an output terminal of the differential amplifier.
In one possible implementation, the coding voltage is a square wave signal or a sine wave signal.
In a second aspect, a touch chip is provided, which includes the capacitance detection circuit in the first aspect or any possible implementation manner of the first aspect.
In a third aspect, an electronic device is provided, including:
a touch screen; and the number of the first and second groups,
the touch chip in the second aspect or any possible implementation manner of the second aspect.
Based on the technical scheme, the capacitance detection circuit is provided with a CCA circuit and a PGA circuit connected with the CCA circuit. The input end of the CCA circuit is respectively connected with the capacitor to be tested and the offset capacitor, and the output end of the CCA circuit respectively outputs corresponding first current and second current. The offset capacitance is smaller than the initial value of the capacitance to be measured, and the ratio between the first current and the second current is set equal to the ratio between the initial value of the capacitance to be measured and the offset capacitance. Therefore, when the capacitor to be measured is the initial value, the output of the PGA circuit is 0, and when the capacitor to be measured changes relative to the initial value, the output of the PGA circuit is related to the capacitance change of the capacitor to be measured. Therefore, the capacitance variation of the capacitor to be detected can be obtained through the output signal of the PGA circuit, and the cost of the capacitance detection circuit is reduced because a smaller offset capacitor can be adopted to offset a larger initial value of the capacitor to be detected.
Drawings
Fig. 1 is a fully differential based capacitance detection circuit.
Fig. 2 is a capacitance detection circuit based on a cancellation capacitance.
Fig. 3 is a schematic diagram of a capacitance detection circuit according to an embodiment of the present application.
Fig. 4 is a schematic diagram of a possible circuit structure of the CCA circuit according to an embodiment of the present application.
Fig. 5 is a schematic diagram of a possible circuit structure of the CCA circuit according to an embodiment of the present application.
Detailed Description
The technical solution in the present application will be described below with reference to the accompanying drawings.
For a capacitive sensor, the larger the capacitance value of the touch screen itself, the more difficult it is to extract a minute capacitance change amount caused by a touch. In order to increase the sensitivity of detection of the capacitance change amount, the voltage input to the touch panel is often selected to be larger. When the capacitance change amount is detected, the capacitance value of the touch panel detected also becomes large. In this case, the capacitance detection circuit is easily saturated. To prevent the capacitance detection circuit from saturating, a higher dynamic range of the circuit is required, which may result in a doubling of the power consumption of the capacitance detection circuit.
Moreover, a large part of the data read by the capacitance detection circuit is the large capacitance of the touch screen itself, and the part of the data is redundant data which does not carry valid information for the capacitance change caused by the touch. In order to achieve a capacitance detection circuit with lower power consumption and higher signal-to-noise ratio and improve the efficiency of storing effective information, the requirement of a large dynamic range can be avoided by some methods at present.
One way is for the front end of the circuit to fully differentiate the data of adjacent read channels. Therefore, adjacent touch screen capacitors are connected to the positive end and the negative end of the differential, and differential mode currents or charges at the two ends are amplified through the differential operational amplifier, so that common-mode signals, interference and noise are suppressed. Because the interference signals received by the adjacent channels are basically the same and the capacitances of the touch screens on the adjacent channels are also similar, the interference signals and the capacitance signals of the touch screens can be effectively inhibited as a common mode, and the requirements of the dynamic range of the capacitance detection circuit are greatly reduced. However, since the differential circuit requires reading data from adjacent channels at the same time, it is often necessary to perform two differences in time to obtain differences between all adjacent channels, and to store and restore the capacitance variation of all channels. For example, as shown in fig. 1, it is assumed that the differential operational amplifier differentiates three detection channels, and two differentiations are performed in a time-sharing manner, so that the capacitance variation corresponding to all detection channels can be obtained. It can be seen that the time-sharing reading of data can lose the refresh rate of touch screen signal reading, so it is very difficult to accept in high refresh rate electronic devices, and the use of differential data in the positioning algorithm of touch detection is yet to be verified.
Another way is to cancel out the large capacitance of the touch screen itself. In this scheme, before the capacitance detection circuit reads the capacitance value, the cancellation circuit cancels the capacitance of the touch screen itself, and subtracts the capacitance of the touch screen itself from the voltage, charge or current domain. After subtracting the large capacitance of the touch screen, the small capacitance variation caused by touch can be read out as an effective signal. For example, as shown in FIG. 2, when the capacitor C to be measuredS1Voltage V of printing codeddA capacitor C for canceling the charge amountTGrounding, then the capacitor C to be measuredS1And a capacitor CTRespectively, of charge above is CS1×VddAnd 0. When charge is counteracted, the capacitor C to be measuredS1And a capacitor CTIs connected to the upper plate, the total charge amount is CS1×Vdd=（CS1+CT）×VCMIn which V isCMIs the common mode voltage at the input of the front-end circuit Gm, i.e. 1/2Vdd. Then, the capacitance CTNeed to be equal to CS1The offset voltage can be the common-mode voltage of the front-end circuit. The capacitance C required for cancellation is increased along with the capacitance of the touch screenTThe chip area of the capacitance detection circuit is increased along with the increase of the capacitance detection circuit, so that the chip cost is high.
Therefore, the application provides a capacitance detection circuit, which can offset a large capacitance of a touch screen by using a small offset capacitance, so that the cost of the capacitance detection circuit is not increased while a small capacitance variation is effectively extracted.
Fig. 3 is a possible circuit configuration of the capacitance detection circuit according to the embodiment of the present application. As shown in fig. 3, the capacitance detection circuit 300 includes a Common mode Control Amplifier (CCA) circuit 310 and a Programmable Gain Amplifier (PGA) circuit 320.
The first input end and the second input end of the CCA circuit 310 are respectively connected to the capacitor 331 to be tested and the cancellation capacitor 332, the third input end of the CCA circuit 310 is connected to the coding voltage, and the first output end and the second output end of the CCA circuit 310 respectively output the first current I1 and the second current I2.
The coding voltage may be, for example, a square wave signal or a sine wave signal.
Two input terminals of the PGA circuit 320 are respectively connected to the first output terminal and the second output terminal of the CCA circuit 310.
The cancellation capacitor 332 is smaller than the initial value of the capacitor to be measured 331.
The ratio between the first current I1 and the second current I2 is set to be equal to the ratio between the initial value of the capacitor under test 331 and the cancellation capacitor 332, so that the output of the PGA circuit 320 is 0 when the capacitor under test is at the initial value, and the output of the PGA circuit 320 is associated with the capacitance change of the capacitor under test when the capacitor under test is changed from the initial value.
It should be understood that, in practical applications, the output of the PGA circuit 320 described in the embodiments of the present application is 0, which may mean that the value of the signal output by the PGA circuit 320 is 0; or that the value of the signal output by the PGA circuit 320 is within the allowable range, the output can be considered to be substantially 0.
In this embodiment, the ratio between the first current I1 and the second current I2 output by the CCA circuit 310 is set to be equal to the ratio between the initial value of the capacitor 331 to be measured and the cancellation capacitor 332. On one hand, the offset capacitor 332 can be smaller than the initial value of the capacitor 331 to be measured by setting the ratio between the first current I1 and the second current I2; on the other hand, since the ratio between the first current I1 and the second current I2 is equal to the ratio between the initial value of the capacitor to be measured 331 and the cancellation capacitor 332, when the capacitor to be measured 331 is equal to the initial value, the output of the PGA circuit 320 is 0, and when the capacitor to be measured 331 changes from the initial value, the output of the PGA circuit 320 is associated with the capacitance change amount of the capacitor to be measured 331. Thus, the capacitance variation of the capacitor 331 to be detected can be obtained according to the output signal of the PGA circuit 320, and the initial value of the larger capacitor 331 to be detected can be offset by using the smaller offset capacitor 332, which also reduces the cost of the capacitance detection circuit.
When the capacitance detection circuit 300 is applied in the touch field, for example, in a touch screen for mutual capacitance detection, the initial value of the capacitor 331 to be detected may be, for example, a capacitance value between a horizontal electrode and a vertical electrode of the touch screen when a finger does not touch the touch screen; the capacitance variation of the capacitor 331 to be measured may be, for example, a capacitance variation of a mutual capacitance value between the horizontal electrode and the vertical electrode of the touch screen relative to the initial value when a finger touches the touch screen, where the capacitance variation is introduced by the finger touch.
The operation of the CCA circuit 310 will be described in detail with reference to fig. 3.
As shown in fig. 3, two input ports of the CCA circuit 310 are respectively connected to the capacitor to be measured 331 and the cancellation capacitor 332. The two output ports of the CCA circuit 310 may output common-mode currents I1 and I2, so that the voltages on the capacitor to be measured 331 and the cancellation capacitor 332 are equal to the common-mode voltage. When the other input port of the CCA circuit 310 is connected with the code printing voltage VDRVIf the capacitance value C of the cancellation capacitor 332 is smallCEqual to the capacitance C of the capacitor 331 to be measuredSI.e. CC=CSThen the common mode current i on the capacitor 331 to be testeds=sCs×VDRVCommon mode current i on the cancellation capacitor 332c=sCc×VDRV. Current isAnd icWill flow out or in from the CCA circuit 310, and the PGA circuit 320 of the subsequent stage will not see the common mode current, so the output of the PGA circuit 320 is close to 0. Wherein，CSThe initial value, or the basic value, of the capacitance 331 to be measured may be, for example, the capacitance of the touch screen itself. When the capacitance value of the capacitor 331 to be measured is at the initial value CSWhen a change is made on the basis of, e.g. from CSChange to CS+ △ C, a differential mode current is generated, the current is inputted to the PGA circuit 320, the voltage variation of the differential output terminal of the PGA circuit 320 reflects the capacitance variation △ C of the capacitor 331 to be measured, and the voltage signal V outputted by the PGA circuit 320 is usedOUTThe capacitance variation △ C of the capacitor 331 to be measured can be obtained.
Further, when the current ratio of the current I1 and the current I2 is set to M: n, the initial value C of the capacitor 331 to be measuredSAnd the capacitance C of the cancellation capacitor 332CThe ratio between M: and N is added. When N is less than M, the large capacitance C of the touch screen can be counteracted by the counteracting capacitance 332 multiplied by N/MSI.e. using CC=(N/M)×CSCounteraction CS. Assuming that M =10N, only C of 1/10 is presentSThe large capacitance load of the touch screen can be offset by using a small-area low-cost chip in the chip.
The embodiment of the present application does not limit the specific structure of the CCA circuit 310, and other common mode control circuits capable of implementing the above functions are all suitable for the present application. Fig. 4 shows one possible circuit configuration of the CCA circuit 310. VNI and VN2 in fig. 4 are voltages corresponding to the first input terminal and the second input terminal of the CCA circuit 310 in fig. 3; VP is the voltage corresponding to the third input terminal, i.e. V in FIG. 3DRV(ii) a VO1 and VO2 are voltages corresponding to two output terminals of the CCA circuit 310 in fig. 3, and corresponding currents are I1 and I2, respectively.
As shown in fig. 4, the output stage of the CCA circuit 310 includes a first circuit unit 311 and a second circuit unit 312. The first circuit unit 311 includes a first PMOS transistor 3111 and a first NMOS transistor 3112, and a drain of the first PMOS transistor 3111, a drain of the first NMOS transistor 3112, and a first output terminal (VO 1) of the CCA circuit 310 are connected to each other. The second circuit unit 312 includes a second PMOS tube 3121 and a second NMOS tube 3122, and a drain electrode of the second PMOS tube 3121, a drain electrode of the second NMOS tube 3122, and a second output terminal (VO 2) of the CCA circuit 310 are connected. The gate voltages of the first PMOS transistor 3111 and the second PMOS transistor 3121 are the same, and the gate voltages of the first NMOS transistor 3112 and the second NMOS transistor 3122 are the same.
The first transistor circuit 311 is used for outputting a first current I1, and the second transistor circuit 312 is used for outputting a second current I2. The magnitudes of the first current I1 and the second current I2 output by the CCA circuit 310 may be controlled by configuring the first circuit unit 311 and the second circuit unit 312 of the output stage of the CCA circuit 310, for example, configuring a Width/Length (W/L) ratio of MOS transistors in the first circuit unit 311 and the second circuit unit 312, or configuring the number of the first circuit unit 311 and the second circuit unit 312, or the like.
For example, by setting the ratio between the width-to-length ratio of the first PMOS transistor 3111 and the first NMOS transistor 3112 in the first circuit unit 331 and the width-to-length ratio of the second PMOS transistor 3121 and the second NMOS transistor 3122 in the second circuit unit 312, the ratio between the first current I1 and the second current I2 is obtained.
Assuming that the width-to-length ratios of the first PMOS transistor 3111 and the first NMOS transistor 3112 are both M: 1, the width-to-length ratios of the second PMOS tube 3121 and the second NMOS tube 3122 are both N: 1, the ratio I1 between the first current I1 and the second current I2 is: i2= M: and N is added.
For another example, by setting the ratio between the number of first circuit units 311 and the number of second circuit units 312 included in the CCA circuit 310, the ratio between the first current I1 and the second current I2 is obtained.
For example, as shown in fig. 5, assuming that the output stage of the CCA circuit 310 includes M first circuit units 311 connected in parallel and N second circuit units 312 connected in parallel, the first circuit units 311 and the second circuit units 312 output a ratio I1 between the first current I1 and the second current I2: i2= M: and N is added.
The ratio between the first current I1 and the second current I2 may be set according to the characteristics of the touch screen, the requirement for cancellation capacitance, and the like, for example, I1: i2 may be located at 5: 1 to 15: 1 such as I1: i2= 10: 1. accordingly, the capacitance value C of the cancellation capacitor 332CMay be the initial value C of the capacitor 331 to be measuredS1/5 to 1 of/15 such as 1/10.
In the embodiment of the present application, the ratio between the first current I1 and the second current I2 output by the CCA circuit 310 may be adjustable. Cancellation capacitor 332 may also be an adjustable capacitor. Wherein, by adjusting the ratio I1 between the first current I1 and the second current I2: i2, and/or adjusting the capacitance value C of the cancellation capacitor 332CThe capacitance value of the capacitor 331 to be measured can be made equal to the initial value CSThe voltage V output by the PGA circuit 320 in the case of (1)OUTIs 0.
A plurality of steps may be provided at the output stage of the CCA circuit 310. For example, a plurality of steps are respectively set for the first circuit unit 311 and the second circuit unit 312, where the width-to-length ratios of the MOS transistors corresponding to different steps are different; for another example, as shown in fig. 5, when the number of first circuit units 311 and the number of second circuit units 312 that are currently required to be connected in parallel are selected by the inhibitor switch, such as when M first circuit units 311 and N second circuit units 312 are selected, I1: i2= M: and N is added. Therefore, initially, the voltage signal V output by the PGA circuit 320 may be adjusted by adjusting the position of the CCA circuit 310 and/or adjusting the capacitance of the cancellation capacitor 332OUTIs substantially 0. Then, in the capacitance detection, if there is a finger touch, the voltage signal V output from the PGA circuit 320 is usedOUTThe capacitance variation of the capacitor 331 to be measured caused by the touch can be known.
As shown in fig. 3, the PGA circuit 320 includes, for example, a differential amplifier PGA, and a feedback capacitor C connected across the input terminal and the output terminal of the differential amplifier PGAFAnd a feedback resistor RF。
The embodiment of the present application further provides a touch chip, which includes the capacitance detection circuit in the various embodiments of the present application.
An embodiment of the present application further provides an electronic device, including: a touch screen; and, the touch chip in the various embodiments of the present application described above.
By way of example and not limitation, the electronic device in the embodiments of the present application may be a portable or mobile computing device such as a terminal device, a mobile phone, a tablet computer, a notebook computer, a desktop computer, a game device, an in-vehicle electronic device, or a wearable smart device, and other electronic devices such as an electronic database, an automobile, and an Automated Teller Machine (ATM). This wearable smart machine includes that the function is complete, the size is big, can not rely on the smart mobile phone to realize complete or partial function, for example: smart watches or smart glasses and the like, and only focus on a certain type of application function, and need to be used in cooperation with other devices such as smart phones, such as various smart bracelets for physical sign monitoring, smart jewelry and other devices.
It should be noted that, without conflict, the embodiments and/or technical features in the embodiments described in the present application may be arbitrarily combined with each other, and the technical solutions obtained after the combination also fall within the protection scope of the present application.
It should be understood that the specific examples in the embodiments of the present application are for the purpose of promoting a better understanding of the embodiments of the present application, and are not intended to limit the scope of the embodiments of the present application, and that various modifications and variations can be made by those skilled in the art based on the above embodiments and fall within the scope of the present application.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present application, and shall be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (10)

1. A capacitance detection circuit, comprising:
a first input end and a second input end of the CCA circuit are respectively connected with a capacitor to be tested and a cancellation capacitor, a third input end of the CCA circuit is connected with a coding voltage, a first output end and a second output end of the CCA circuit respectively output a first current and a second current, and the cancellation capacitor is smaller than an initial value of the capacitor to be tested;
the two input ends of the PGA circuit are respectively connected with the first output end and the second output end of the CCA circuit;
wherein a ratio between the first current and the second current is set equal to a ratio between an initial value of the capacitance to be measured and the offset capacitance, so that an output of the PGA circuit is 0 when the capacitance to be measured is the initial value, and the output of the PGA circuit is associated with a capacitance variation amount of the capacitance to be measured when the capacitance to be measured is varied with respect to the initial value.
2. The capacitance detection circuit according to claim 1, wherein the output stage of the CCA circuit includes a first circuit unit and a second circuit unit,
the first circuit unit comprises a first PMOS tube and a first NMOS tube, the drain electrode of the first PMOS tube, the drain electrode of the first NMOS tube and the first output end of the CCA circuit are connected,
the second circuit unit comprises a second PMOS tube and a second NMOS tube, the drain electrode of the second PMOS tube, the drain electrode of the second NMOS tube and the second output end of the CCA circuit are connected,
the grid voltages of the first PMOS tube and the second PMOS tube are the same, and the grid voltages of the first NMOS tube and the second NMOS tube are the same.
3. The capacitance detection circuit according to claim 2, wherein the ratio between the first current and the second current is obtained by setting a ratio between a width-to-length ratio of the first PMOS transistor and the first NMOS transistor and a ratio between a width-to-length ratio of the second PMOS transistor and the second NMOS transistor.
4. The capacitance detection circuit according to claim 2, wherein a ratio between the first current and the second current is obtained by setting a ratio between the number of the first circuit units and the number of the second circuit units included in the CCA circuit.
5. The capacitance detection circuit according to any one of claims 1 to 4, wherein a ratio between the first current and the second current output by the CCA circuit is adjustable, and the cancellation capacitance is an adjustable capacitance, wherein the output of the PGA circuit is 0 when the capacitance to be measured is at the initial value by adjusting the ratio between the first current and the second current and/or the cancellation capacitance.
6. The capacitance detection circuit according to any one of claims 1 to 4, wherein a ratio between the first current and the second current is in a range of 5: 1 to 10: 1.
7. The capacitance detection circuit according to any one of claims 1 to 4, wherein the PGA circuit comprises a differential amplifier, and a feedback capacitor and a feedback resistor connected across the input and output terminals of the differential amplifier.
8. The capacitance detection circuit according to any one of claims 1 to 4, wherein the coding voltage is a square wave signal or a sine wave signal.
9. A touch chip comprising the capacitance detection circuit of any one of claims 1 to 8.
10. An electronic device, comprising:
a touch screen; and the number of the first and second groups,
the touch chip of claim 9.
CN202010487566.7A 2020-06-02 2020-06-02 Capacitance detection circuit, touch chip and electronic equipment Active CN111399704B (en)

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CN114691439B (en) * 2022-05-31 2022-08-26 上海泰矽微电子有限公司 Capacitive touch detection chip circuit capable of expanding channel and detection method

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Publication number Priority date Publication date Assignee Title
CN108124474A (en) * 2017-01-18 2018-06-05 深圳市汇顶科技股份有限公司 Detect the device, electronic equipment and the device for detecting pressure of capacitance
CN108475155A (en) * 2018-03-30 2018-08-31 深圳市为通博科技有限责任公司 Capacitive detection circuit, touch detecting apparatus and terminal device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108124474A (en) * 2017-01-18 2018-06-05 深圳市汇顶科技股份有限公司 Detect the device, electronic equipment and the device for detecting pressure of capacitance
CN108475155A (en) * 2018-03-30 2018-08-31 深圳市为通博科技有限责任公司 Capacitive detection circuit, touch detecting apparatus and terminal device

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