Array resistor coupling crosstalk suppression circuit based on improved isopotential method

Abstract

The invention relates to the technical field of analog circuits, and discloses an array resistor coupling crosstalk suppression circuit based on an improved isopotential method, which comprises an array resistor, a row multiplexer switch, a column multiplexer switch, a driving operational amplifier, a bias operational amplifier, a reading operational amplifier, a feedback resistor RF, a feedback capacitor CF, a driving voltage VDRIVE and a bias voltage VREF, the row multi-path selection switch is a switch combination with three switches in each row, and the column multi-path selection switch is a switch combination with three switches in each column; by improving a circuit connection mode and a signal reading scheme in an existing equipotential circuit, coupling crosstalk caused by on resistance of a row-column gating switch, input offset voltage of an integrated operational amplifier and limited open-loop gain is remarkably eliminated, and the accuracy of a system is improved.

Description

Technical Field

[0001] The invention relates to the technical field of analog circuits, and in particular to an array resistor coupling crosstalk suppression circuit based on an improved equipotential method. Background Art

[0002] Array resistors are widely used in fields such as tactile sensing, gas detection, and infrared sensing. They are a widely used method for measuring physical variables. The coupling crosstalk in array resistors refers to the phenomenon that when an electrical signal is transmitted in one resistor channel, it is interfered by other resistor channels and non-ideal characteristics of the circuit, causing the electrical signal to change, thereby reducing the accuracy and reliability of the system. This is due to the circuit structure of the array resistors sharing rows and columns. Although the traditional equipotential circuit eliminates crosstalk to a certain extent based on the equipotential principle, the non-ideal characteristics of the circuit, including the on-resistance of the row and column selection switches, the input offset voltage of the integrated operational amplifier, and the limited open-loop gain, etc., cause inevitable additional crosstalk. Therefore, how to effectively suppress the coupling crosstalk caused by these non-ideal characteristics of the circuit, thereby improving the reliability of the array resistor system, has become a problem that needs to be solved urgently in this field. Summary of the invention

[0003] The purpose of the present invention is to eliminate the coupling crosstalk caused by the non-ideal characteristics of the circuit in the existing equipotential circuit, and to provide an array resistor coupling crosstalk suppression circuit based on the improved equipotential method. The present invention significantly eliminates the coupling crosstalk caused by the on-resistance of the row and column selection switches, the input offset voltage of the integrated operational amplifier and the limited open-loop gain by improving the circuit connection method and signal reading scheme in the existing equipotential circuit.

[0004] In order to achieve the above-mentioned purpose, the present invention provides an array resistor coupling crosstalk suppression circuit based on an improved equipotential method, comprising array resistors, row multiplexers, column multiplexers, a driving operational amplifier, a biasing operational amplifier, a readout operational amplifier, a feedback resistor RF, a feedback capacitor CF, a driving voltage V_DRIVE, and a biasing voltage V_REF. The row multiplexers are a switch combination of three switches for each row, and the column multiplexers are a switch combination of three switches for each column.

[0005] Preferably, the array resistor is an array having M rows and N columns of variable resistors, each row of the array resistor has a row conductor connected to one end of all the resistors in the row, and each column of the array resistor has a column conductor connected to the other end of all the resistors in the column.

[0006] Preferably, one end of the three switches in each row of the row multi-way selection switches is connected to the row conductor of the array resistor in the row, and the other end of the three switches in each row of the row multi-way selection switches is respectively connected to the inverting input terminal of the driving operational amplifier, the output terminal of the driving operational amplifier and the reverse input terminal of the bias operational amplifier.

[0007] Preferably, the positive input terminal of the driving operational amplifier is connected to a driving voltage V_DRIVE.

[0008] Preferably, one end of the three switches in each column of the column multiplexer is connected to the column conductor of the array resistor in the column, and the other end of the three switches in each column of the column multiplexer is respectively connected to the inverting input terminal of the readout operational amplifier, the output feedback terminal of the readout operational amplifier and the output terminal of the bias operational amplifier.

[0009] Preferably, the positive input terminal of the readout operational amplifier is connected to a bias voltage V_REF.

[0010] Preferably, the non-inverting input terminal of the bias operational amplifier is connected to the bias voltage V_REF.

[0011] Preferably, the smoking behavior detection is implemented by combining distance determination and multi-frame determination.

[0012] Preferably, when reading the array resistance signal, among the switches of the rows and columns corresponding to the target read resistance, the two switches connected to the driving operational amplifier and the two switches connected to the read operational amplifier are in a closed state, while the switch connected to the bias operational amplifier is in an open state; while the switches corresponding to the other rows and columns, connecting the driving operational amplifier and the read operational amplifier, are in an open state, and the switch connected to the bias operational amplifier is in a closed state.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] 1. The present invention connects the reverse input terminal of the driving operational amplifier to the output terminal through a switch, thereby ensuring that the row signal of the array resistor is accurately biased to V_DRIVE, and ensuring that the existence of the on-resistance of the row multiplexer switch does not affect the size of the row signal of the array resistor, thereby curbing the generation of crosstalk current.

[0015] 2. The present invention connects the reverse input terminal of the readout operational amplifier to the output feedback terminal through a switch, ensuring that the column signal of the array resistor is accurately biased to V_REF, and ensuring that the existence of the on-resistance of the column multi-way selection switch will not affect the size of the array resistor column signal, thereby improving the accuracy of the system.

[0016] 3. The present invention connects the reverse input terminal of the bias operational amplifier to the non-target readout row in the array resistor, ensuring that the voltage signal between the non-target readout row and the target readout column is the external voltage V_REF, so that the voltage difference of the non-target readout resistor is 0.

[0017] 4. The present invention adopts double sampling technology to eliminate the crosstalk caused by the operational amplifier input bias voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the equipotential circuit diagram proposed by the present invention;

[0019] Figure 2 It is a traditional equipotential circuit diagram;

[0020] Figure 3 It is an equipotential circuit diagram using a biased op amp for equipotential biasing;

[0021] Figure 4 It is a comparison diagram of the conventional equipotential circuit and the equipotential circuit of the present invention in the manner of connecting the multi-way selection switch in the driving operational amplifier and the readout operational amplifier;

[0022] Figure 5 It is a comparison diagram of an equipotential circuit using a biased operational amplifier for equipotential biasing and an equipotential circuit proposed by the present invention in which the biased operational amplifier is connected to a multi-way selection switch;

[0023] Figure 6 is an equivalent circuit diagram of the equipotential circuit diagram proposed by the present invention;

[0024] Figure 7 This is the error result diagram of three equipotential circuits after simulation using PSPICE software under different switch on-resistance conditions;

[0025] Figure 8 This is the error result diagram of three equipotential circuits after simulation using PSPICE software under different op amp gains;

[0026] Fig. 9 This is the error result diagram of three equipotential circuits after simulation using PSPICE software under different op amp input bias voltage conditions;

[0027] Fig.10 This is a diagram of error results after the equipotential circuit of the present invention is simulated using PSPICE software after adopting a double sampling algorithm. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] To explain the specific implementation of the present invention in detail, the present invention will make circuits equivalent and use some circuit symbols to represent the voltage, resistance and current of some nodes to facilitate the calculation of the magnitude of the crosstalk current. At the same time, to better present the superiority of the present invention, it will be compared with the traditional method. The present invention compares the traditional equipotential circuit and the biased op amp equipotential circuit, respectively. Figure 2 and Figure 3 As shown, the simulation analysis was carried out using PSPICE simulation software.

[0030] The present invention discloses an array resistor coupling crosstalk suppression circuit based on an improved equipotential method, which is an equipotential circuit improved based on the equipotential method. Figure 1 As shown, it includes array resistors, row multiplexer switches, column multiplexer switches, a driving operational amplifier, a biasing operational amplifier, a readout operational amplifier, a feedback resistor RF, a feedback capacitor CF, a driving voltage V_DRIVE, and a bias voltage V_REF.

[0031] The array resistor is an array of variable resistors with M rows and N columns, each row of the array resistor has a row conductor connected to one end of all the resistors in the row, and each column of the array resistor has a column conductor connected to the other end of all the resistors in the column.

[0032] In the row multiplexer switches, each three switches form a group connected to the row conductors of the array resistors, and the three switches are respectively connected to the inverting input terminal and output terminal of the driving operational amplifier and the reverse input terminal of the biasing operational amplifier.

[0033] The reverse input terminal and the output terminal of the driving operational amplifier are connected to the row multiplexer, respectively connected to two switches among the three switches corresponding to each row in the row multiplexer switch, and the forward input terminal is connected to the driving voltage V_DRIVE.

[0034] In the column multiplexer switches, each three switches form a group connected to the column conductors of the array resistor, and the three switches are respectively connected to the inverting input terminal, the output feedback terminal and the output terminal of the bias operational amplifier.

[0035] The inverting input terminal and the output feedback terminal of the readout operational amplifier are connected to the column multiplexer, and are respectively connected to two of the three switches corresponding to each column in the column multiplexer switch, where the feedback resistor and the feedback capacitor are RF and CF respectively, and the positive input terminal is connected to the bias voltage V_REF.

[0036] The bias operational amplifier has a reverse input terminal connected to the last switch of three switches corresponding to each row in the row multiplexer, an output terminal connected to the last switch of three switches corresponding to each column in the column multiplexer, and a forward input terminal connected to the bias voltage V_REF.

[0037] The present invention is relative to Figure 2 The circuit has a better crosstalk suppression effect. To express the crosstalk suppression effect more intuitively, Figure 4 The two circuits are compared. In the figure, Ron represents the resistance of the switch on-resistance, and I represents the current value.

[0038] Figure 2 In the circuit, the driving operational amplifier directly connects the reverse input terminal and the output terminal of the operational amplifier to the switch, and the on-resistance will have a current, thereby causing a voltage drop that affects the output result; in the present invention, due to the "virtual off" characteristic of the driving operational amplifier, the current of the switch connected to the reverse input terminal of the operational amplifier is close to 0, so the size of the connection array row and column signals is accurately biased to V_DRIVE and V_REF, thereby improving the accuracy of the system output result. Figure 2 In the circuit, the output of the operational amplifier is connected to the reverse output terminal of the operational amplifier through a feedback resistor, and then connected to a switch. Current will also appear in the switch, causing a voltage drop. However, in the circuit of the present invention, due to the "virtual disconnection" characteristic of the circuit, the column signal can be accurately biased to V_REF.

[0039] The present invention is relative to Figure 3 The circuit also has a better crosstalk suppression effect. To express the crosstalk suppression effect more intuitively, Figure 5 The two circuits are compared. In the figure, Ron represents the on-resistance of the switch, I represents the current flowing through the row switch, and IXT represents the crosstalk current value.

[0040] For the biased operational amplifier, the present invention connects the switches of the rows and columns between the reverse input terminal and the output terminal of the operational amplifier. For example, when reading the signal value of the resistor R11, due to the "virtual short" characteristic of the operational amplifier, the voltages of the 2nd to Mth rows of the array are all V_REF. Since the voltage of the first column is also V_REF, no current will flow to the first column except R11, thereby suppressing the crosstalk current.

[0041] The circuit of the present invention will be theoretically analyzed below. To simplify the calculation, the circuit conditions are assumed as follows: the target read resistance is R11 , the resistance of all other resistors in the array is R ij , except for the first row, all row signal voltages are the same and are equivalent to a node ROWX, except for the first column, all column signal voltages are the same and are equivalent to a node COLX, the gain of all op amps is A, and the on-resistance of all switches is R on The input bias voltages of the driving operational amplifier, the readout operational amplifier, and the bias operational amplifier are V OSD , V OS1 , V OS2 , the output voltage of the operational amplifier is read as V OUT , the output voltage of the bias op amp is V BO , the magnitude of the crosstalk current is I XT Among them, R ONN and R ONM They are the parallel resistances of the row and column switches connected to the bias op amp respectively.

[0042] In the simplified circuit diagram, R D , R E , R G and R ONN and R ONM The expressions are:

[0043]

[0044] Crosstalk current I XT for:

[0045]

[0046] According to Kirchhoff's voltage law, the output V of the biased operational amplifier can be obtained BO for:

[0047]

[0048] By V BO It can be seen from the expression that V BO A、V OS2 , R ONN and R D The influence of R ONN The expressions of and RD show that they are much smaller than R ON and R ij The resistance value of A is also very large, so V BO A、R ONN and R D The impact is very small. XT It can be found in the expression of V BO The value of will be divided by A, so A, RONN and R D The effect on the crosstalk current is minimal, but the input bias voltages of the bias op amp and the sense op amp still cause significant crosstalk.

[0049] In terms of sampling method, the present invention uses a double sampling method. The principle of this method is to use two different driving voltages to drive the circuit to obtain two output voltages, and then use the two output voltages to perform calculations to obtain an accurate target resistance value.

[0050] Using two driving voltages V DRV1 and V DRV2 Drive them separately, and the output voltages are V OUT1 and V OUT2 , according to Kirchhoff's current law, two expressions can be obtained:

[0051]

[0052] By subtracting the two equations, we can get the accurate resistance value R of the measured resistor. MEAS :

[0053]

[0054] To verify the superiority of the present invention in crosstalk suppression, the circuit is simulated using PSPICE simulation software. The simulation conditions are as follows: the simulated array size is 10×10, the target readout resistor is R11, the resistance is 1MΩ, V REF The value is 0.4V, V DRIVE The value is 0.3V, and the scanning array resistance R ij Different switch on-resistance R from 1kΩ to 1MΩ ON , the limited open-loop gain A of the op amp and the input bias voltage VOS affect the simulation results. Set A to 80dB, 100dB, 120dB, 140dB, and 160dB respectively, and set R ON 0Ω, 2Ω, 5Ω, 10Ω respectively, set V OS1 They are 0uV, -0.1uV, -1uV, -10uV, -100uV, and 1mV respectively.

[0055] Using R ERROR To judge the accuracy of the simulation results, R ERROR is the error percentage between the actual value and the read value of the target read resistance, where R MEAS The measured R 11 The resistance value, R TRUE For R 11 The actual resistance value. According to the circuit diagram, R MEAS The value of VOUT The value of R ERROR and R MEAS The expressions are:

[0056]

[0057] To analyze the switch on resistance R ON The influence on the accuracy of the results is shown in the following figure. Using the method of controlling variables, the input bias voltage of the op amp is set to 0 and the gain A of the op amp is set to 160dB. The simulation results of the three circuit diagrams are as follows: Figure 7 As shown in the simulation results, it can be seen that the switch on-resistance of the biased op amp equipotential circuit has the greatest impact on the simulation results. When the resistance value of Rij is small, R ON When the resistance is 10Ω, the error is as high as 80%, even if R ON The resistance value is 2Ω, and the error is also about 10%; the traditional equipotential circuit has only a row switch, so the impact on the accuracy of the result is small, and the error is within 10% under various resistance values; the error of the equipotential circuit of the present invention is extremely small, reaching less than 0.2%. Therefore, the simulation results confirm the effectiveness of the present invention in suppressing crosstalk caused by switch on-resistance.

[0058] Similarly, the limited open-loop gain of the op amp is analyzed using the control variable method. Assume that the switch on resistance R ON The input bias voltage of the op amp is also 0, and the simulation results of the three circuit diagrams are as follows: Figure 8 As shown, from Figure 8 The simulation results of the traditional equipotential circuit show that the error increases with R ij The increase of R ij When A is 10k, it gradually stabilizes to about 0. The smaller A is, the greater the error is. When A is 80dB and R ij In the low resistance range, the error exceeds 80%, which shows that the open-loop voltage gain of the op amp greatly affects the accuracy of the circuit reading. The simulation results of the biased op amp equipotential circuit and the equipotential circuit of the present invention are very similar. The error increases with R ij The increase in A is very small, and the error is also very small. Even if the value of A is as low as 80dB, the error is still less than 6%. When A is above 100dB, the error is even less than 1%. This result proves that the biased operational amplifier equipotential circuit and the equipotential circuit of the present invention can effectively suppress the crosstalk caused by the limited open-loop gain of the operational amplifier.

[0059] When simulating and analyzing the input bias voltage of the op amp, the switch on-resistance is set to 0 and the limited open-loop gain of the op amp is set to 160dB. To simulate the worst result, set V OS2 The value is -V OS1 ,The simulation results of the three circuits are as follows Fig. 9 As shown in the figure, the simulation results of the three circuits are very close. The simulation results show that the input bias voltage has a great influence on the accuracy of the results. When the input bias voltage V OS1 When the value is -1mV, the read error is greater than 100mV, and as R ij Therefore, the proposed improved equipotential circuit does not solve the crosstalk caused by the input bias voltage of the operational amplifier, so other methods are needed to solve the crosstalk problem caused by this non-ideal characteristic.

[0060] The double sampling method uses two driving voltages to drive the circuit. DRIVE Based on the result obtained with 0.3V, another driving voltage V DRIVE The equipotential circuit of the present invention is driven by 0.5V, and then the simulation results are double sampled. The results are as follows: Fig.10 As shown in the figure, it can be seen that no matter what the input bias voltage of the op amp is, the simulation error is close to 0, thus verifying the correctness of the double sampling method. This method effectively solves the coupling crosstalk caused by the input bias voltage of the op amp.

[0061] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. An array resistor coupling crosstalk suppression circuit based on an improved equipotential method, comprising an array resistor, a row multiplexer, a column multiplexer, a driving operational amplifier, a biasing operational amplifier, a readout operational amplifier, a feedback resistor RF, a feedback capacitor CF, a driving voltage V_DRIVE, and a biasing voltage V_REF, characterized in that: The row multi-way selection switch is a switch combination of three switches in each row, and the column multi-way selection switch is a switch combination of three switches in each column.

2. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 1 is characterized in that: The array resistor is an array of variable resistors with M rows and N columns, each row of the array resistor has a row conductor connected to one end of all the resistors in the row, and each column of the array resistor has a column conductor connected to the other end of all the resistors in the column.

3. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 2 is characterized in that: One end of the three switches in each row of the row multi-way selection switches is connected to the row conductor of the array resistor in the row, and the other end of the three switches in each row of the row multi-way selection switches is respectively connected to the inverting input terminal of the driving operational amplifier, the output terminal of the driving operational amplifier and the reverse input terminal of the bias operational amplifier.

4. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 3 is characterized in that: The positive input terminal of the driving operational amplifier is connected to the driving voltage V_DRIVE.

5. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 4 is characterized in that: One end of the three switches in each column of the column multiplexer is connected to the column conductor of the array resistor in the column, and the other end of the three switches in each column of the column multiplexer is respectively connected to the inverting input terminal of the readout operational amplifier, the output feedback terminal of the readout operational amplifier and the output terminal of the bias operational amplifier.

6. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 5, characterized in that: The positive input terminal of the readout operational amplifier is connected to the bias voltage V_REF.

7. The array resistor coupled crosstalk suppression circuit based on the improved equipotential method according to claim 6, characterized in that: The positive input terminal of the bias operational amplifier is connected to the bias voltage V_REF.

8. The array resistor coupling crosstalk suppression circuit based on the improved equipotential method according to claim 7, characterized in that: When reading the array resistance signal, among the switches of the rows and columns corresponding to the target read resistance, the two switches connected to the driving operational amplifier and the two switches connected to the read operational amplifier are in a closed state, while the switch connected to the bias operational amplifier is in an open state; while the switches corresponding to the other rows and columns connecting the driving operational amplifier and the read operational amplifier are in an open state, and the switch connected to the bias operational amplifier is in a closed state.

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