WO2024156099A1

WO2024156099A1 - Nanowire electrode impedance measurement circuit for dedicated chip for retinal prosthesis, and chip

Info

Publication number: WO2024156099A1
Application number: PCT/CN2023/073595
Authority: WO
Inventors: 闫祎峰; 王昊; 吴天准
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2023-01-28
Filing date: 2023-01-28
Publication date: 2024-08-02

Abstract

The present disclosure relates to the technical field of chip circuits, in particular to a nanowire electrode impedance measurement circuit for a dedicated chip for a retinal prosthesis. The circuit comprises a measurement probe module and a voltage driving module. An input end of the measurement probe module is connected to an output end of a stimulation voltage, and an output end of the measurement probe module is connected to an input end of the voltage driving module. The measurement probe module comprises a voltage division unit and a voltage attenuation unit, the voltage division unit comprising an adjustable voltage division resistor and a plurality of control switches. The voltage attenuation unit comprises a voltage attenuation capacitor and a plurality of control output switches; by means of controlling the on-off states of the plurality of control output switches, the voltages at two nodes generating voltage drop at two ends of the adjustable voltage division resistor are respectively obtained; and by means of a voltage division effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to be within an input voltage range of the voltage driving module. The present invention is used for measuring impedance values of nanowire electrode arrays, achieving real-time measurement of the impedance of bioelectrodes.

Description

Nanowire electrode impedance detection circuit and chip for retinal prosthesis dedicated chip

Technical Field

The embodiments of the present application relate to the field of chip circuit technology, and in particular to a nanowire electrode impedance detection circuit and chip for a retinal prosthesis dedicated chip.

Background technique

Currently, AMD (age-related macular degeneration) and RP (retinitis pigmentosa) are two common retinal diseases, which usually occur in the elderly (the former) and teenagers (the latter), and these diseases cannot be cured by drugs. The only cure is to implant a retinal prosthesis, bypassing the damaged photoreceptors and directly connecting to the remaining retinal neurons to help patients with retinal damage restore vision. The most important thing in the retinal prosthesis system is the implantable retinal prosthesis chip, which needs to receive external data and energy and control the generation of a constant stimulation voltage. Compared with other implanted chips, retinal prostheses need to meet more stringent requirements, such as smaller chip area, stable output voltage stimulation, and high reliability and safety.

Traditional retinal prostheses require the implantation of flexible electrodes and use chip active control for stimulation; the flexible electrodes of the new generation of retinal prostheses are nanowire arrays, which have the advantages of light control and high density. Light control refers to the control of the impedance of the nanowire electrodes by the light spot, thereby controlling the state of stimulation. The high-density nanowire array greatly improves the resolution. The structural diagrams of the two systems are shown in Figure 1. The new generation of nanowire retinal prostheses can not only improve the resolution, but also break through the limitation of the number of traditional flexible electrodes, and control the intensity of stimulation through constant voltage stimulation and the photosensitivity of nanowire electrodes.

In existing retinal prosthesis chips, most sensor modules only include temperature detection functions, and rarely detect the impedance value of electrodes. In addition, there is no retinal prosthesis chip for nanowire array electrodes. However, the test of electrode impedance plays a very important role in the performance of retinal prosthesis. Therefore, it is urgent to propose a detection circuit for detecting the impedance of nanowire electrodes of retinal prosthesis chips to determine the working state of nanowire electrode implants, in order to adapt to the changes of its nanowire electrodes, and to achieve a wider detection range on the basis of traditional retinal prosthesis chip impedance detection.

Summary of the invention

The embodiments of the present application provide a nanowire electrode impedance detection circuit and chip for a retinal prosthesis-specific chip, which are used to detect the impedance value of a nanowire electrode array, and can realize real-time detection of the impedance size of a biological electrode to ensure that the nanowire electrode is working normally and in good contact with the retinal neural tissue.

In order to solve the above technical problems, in the first aspect, the embodiment of the present application provides a nanowire electrode impedance detection circuit of a retinal prosthesis dedicated chip, including: a detection probe module and a voltage driving module; the input end of the detection probe module is connected to the output end of the stimulation voltage, the output end of the detection probe module is connected to the input end of the voltage driving module, and the output end of the voltage driving module is connected to the input end of the stimulation voltage. The detection probe module includes a voltage divider unit and a voltage attenuation unit. The voltage divider unit includes an adjustable voltage divider resistor and a plurality of control switches. By controlling the switch states of the plurality of control switches, the adjustable voltage divider resistor is connected to the path of the stimulation current, so that the adjustable voltage divider resistor and the electrode divide the voltage, and a voltage drop is generated at both ends of the adjustable voltage divider resistor. The voltage attenuation unit includes a voltage attenuation capacitor and a plurality of control output switches. By controlling the switch states of the plurality of control output switches, the voltages at two nodes where the voltage drop is generated at both ends of the adjustable voltage divider resistor are respectively obtained. Through the voltage dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module.

In some exemplary embodiments, the voltage attenuation capacitor includes a first capacitor and a second capacitor connected in parallel, and a first adjustable capacitor and a second adjustable capacitor arranged between the output end of the first capacitor and the output end of the second capacitor; the control output switch includes two, the input ends of the two control output switches are respectively connected to the output end of the first capacitor and the output end of the second capacitor, and the first adjustable capacitor and the second adjustable capacitor are located between the input ends of the two control output switches.

In some exemplary embodiments, the control switch of the voltage dividing unit includes a first switch, a second switch and a third switch, the input end of the first switch is connected to the output end of the stimulation voltage, and the output end of the first switch is connected to the nanowire electrode; the second switch and the third switch are respectively connected in parallel at both ends of the first switch, and the adjustable voltage dividing resistor is arranged between the output end of the second switch and the output end of the third switch.

In some exemplary embodiments, the first switch, the second switch, and the third switch are all detection mode control switches.

In some exemplary embodiments, two nodes at which a voltage drop is generated at both ends of the adjustable voltage-dividing resistor are respectively recorded as node A and node B; through the voltage-dividing effect of the voltage-attenuating capacitor, the voltages at node A and node B are respectively attenuated to within the input voltage range of the voltage driving module, and the nodes after the voltage reduction are respectively recorded as node A' and node B';

When the voltage attenuation coefficient is a certain value, the resistance of the nanowire resistor is obtained by formula (1):

Wherein, R _electrode represents the resistance of the nanowire, R _s represents the adjustable voltage divider resistance, _VA represents the voltage at the node A, _VB represents the voltage at the node B, _VA ' represents the voltage at the node A' after voltage reduction, and _VB ' represents the voltage at the node B' after voltage reduction.

In some exemplary embodiments, the attenuation voltage value is set according to the voltage value of the stimulation voltage, and the attenuated voltage value is made to be within the input voltage range of the voltage driving module through capacitor voltage division; there is a voltage division point in the voltage attenuation path between the first capacitor and the first adjustable capacitor, which is denoted as V _x , and the expression of the voltage division point s domain is shown in formula (2):

Considering the influence of the parasitic resistance of the switch, the parasitic resistance of the switch is added between the first capacitor and the voltage dividing point, and formula (3) is obtained:

Wherein, _Vx represents the voltage at the voltage dividing point, _Vs represents the voltage value of the stimulation voltage, _C1 represents the first capacitor, _C2 represents the first adjustable capacitor, _R1 represents the added switch parasitic resistance, and _R2 represents the switch parasitic resistance.

In some exemplary embodiments, the resistance of the adjustable voltage divider resistor is 10k, 100k or 1M.

In some exemplary embodiments, the stimulation voltage is outputted by a voltage stimulator; the voltage value of the stimulation voltage is ±5V, ±9V or ±12V.

In some exemplary embodiments, the input voltage range of the voltage driving module is 0.6V to 1.2V.

In a second aspect, an embodiment of the present application further provides a retinal prosthesis-specific chip, including the nanowire electrode impedance detection circuit of the retinal prosthesis-specific chip described in any of the above embodiments.

The technical solution provided by the embodiment of the present application has at least the following advantages:

The embodiment of the present application provides a nanowire electrode impedance detection circuit and chip for a retinal prosthesis dedicated chip, the detection circuit includes a detection probe module and a voltage driving module; the input end of the detection probe module is connected to the output end of the stimulation voltage, the output end of the detection probe module is connected to the input end of the voltage driving module, and the output end of the voltage driving module is connected to the input end of the analog-to-digital conversion circuit; the detection probe module includes a voltage dividing unit and a voltage attenuation unit, the voltage dividing unit includes an adjustable voltage dividing resistor and a plurality of control switches, by controlling the switching states of the plurality of control switches, the adjustable voltage dividing resistor is connected to the path of the stimulation current, the adjustable voltage dividing resistor and the electrode are voltage-divided, and a voltage drop is generated at both ends of the adjustable voltage dividing resistor; the voltage attenuation unit includes a voltage attenuation capacitor and a plurality of control output switches, by controlling the switching states of the plurality of control output switches, the voltages at two nodes where the voltage drop is generated at both ends of the adjustable voltage dividing resistor are respectively obtained; through the voltage dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module.

The present application provides a nanowire electrode impedance detection circuit for a retinal prosthesis dedicated chip, which can be integrated into a retinal prosthesis dedicated chip, and the impedance of the nanowire electrode is monitored in real time through the detection circuit to determine the working state of the retinal prosthesis, so as to ensure that the nanowire electrode is working normally and in good contact with the retinal nerve tissue. According to the multi-level voltage stimulation application scenario and the characteristics of the resistance value range of the nanowire, the present application designs an impedance detection circuit with a configurable voltage domain, and the resistance measurement range is increased from 5kohm-20Mohm. The relative accuracy is high near the small impedance value to be measured, and the accuracy becomes low at high impedance values, which is in line with the resistance change characteristics of the nanowire.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Unless otherwise stated, the pictures in the drawings do not constitute proportional limitations.

FIG1 is a schematic diagram showing a comparison of the structures of a traditional retinal prosthesis and a new generation retinal prosthesis;

FIG2 is a schematic diagram of the structure of a nanowire electrode impedance detection circuit of a retinal prosthesis dedicated chip provided in one embodiment of the present application;

FIG3 is a waveform diagram of a stimulation voltage for input impedance detection provided by an embodiment of the present application;

FIG4 is a schematic diagram and an equivalent circuit diagram of an adjustable capacitor;

FIG5 is a schematic diagram of an improved adjustable capacitor circuit provided in an embodiment of the present application;

FIG6 is a simulation circuit diagram provided by an embodiment of the present application;

FIG. 7 is a diagram of simulation results provided in an embodiment of the present application.

Detailed ways

As can be seen from the background art, in existing retinal prosthesis chips, most sensor modules only include a temperature detection function, and rarely detect the impedance value of the electrode.

In response to this technical problem, an embodiment of the present application provides a nanowire electrode impedance detection circuit for a retinal prosthesis dedicated chip, including: a detection probe module and a voltage driving module; the input end of the detection probe module is connected to the output end of the stimulation voltage, the output end of the detection probe module is connected to the input end of the voltage driving module, and the output end of the voltage driving module is connected to the input end of the analog-to-digital conversion circuit; the detection probe module includes a voltage dividing unit and a voltage attenuation unit, the voltage dividing unit includes an adjustable voltage dividing resistor and a plurality of control switches, by controlling the switching states of the plurality of control switches, the adjustable voltage dividing resistor is connected to the path of the stimulation current, so that the adjustable voltage dividing resistor and the electrode divide the voltage, and a voltage drop is generated at both ends of the adjustable voltage dividing resistor; the voltage attenuation unit includes a voltage attenuation capacitor and a plurality of control output switches, by controlling the switching states of the plurality of control output switches, the voltages at two nodes where the voltage drop is generated at both ends of the adjustable voltage dividing resistor are respectively obtained; through the voltage dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module. The embodiment of the present application detects the impedance value of the nanowire electrode array through the detection circuit, which can realize real-time detection of the impedance size of the biological electrode to ensure that the nanowire electrode works normally and has good contact with the retinal nerve tissue.

The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, those skilled in the art will appreciate that in the various embodiments of the present application, many technical details are provided in order to enable readers to better understand the present application. Yes, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in this application can be implemented.

Referring to FIG. 2 , an embodiment of the present application provides a nanowire electrode impedance detection circuit for a retinal prosthesis dedicated chip, comprising: a detection probe module 101 and a voltage driving module 102; an input end of the detection probe module 101 is connected to an output end of a stimulation voltage Vs, an output end of the detection probe module 101 is connected to an input end of the voltage driving module 102, and an output end of the voltage driving module 102 is connected to an input end of an analog-to-digital conversion circuit (ADC circuit); the detection probe module 101 comprises a voltage dividing unit 1011 and a voltage attenuation unit 1012, and the voltage dividing unit 1011 comprises an adjustable voltage dividing resistor Rs and a plurality of control switches. By controlling the switching states of several control switches, the adjustable voltage-dividing resistor Rs is connected to the path of the stimulation current, so that the adjustable voltage-dividing resistor Rs and the electrode divide the voltage, and a voltage drop is generated at both ends of the adjustable voltage-dividing resistor Rs (node A and node B in FIG. 2 ); the voltage attenuation unit 1012 includes a voltage attenuation capacitor and several control output switches. By controlling the switching states of several control output switches, the voltages at the two nodes where the voltage drop is generated at both ends of the adjustable voltage-dividing resistor Rs are respectively obtained; through the voltage-dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module 102.

As shown in Fig. 2, the control switch includes three detection mode control switches, namely the first switch S1, the second switch S2, and the third switch S3. The control output switch includes two time-sharing control output switches, namely the fourth switch S4 and the fifth switch S5.

This application aims at a new nanowire electrode, improves the original retinal prosthesis chip, and provides a nanowire electrode impedance detection circuit integrated in the retinal prosthesis chip for the application scenarios and working impedance value range of the nanowire electrodes. The impedance value of the nanowire electrode of the retinal prosthesis system is detected. The detection of the electrode impedance value can effectively detect the working state of the implant, thereby determining the working state of the retinal prosthesis system to ensure that the nanowire electrode is working normally and is in good contact with the retinal neural tissue.

The detection circuit structure of the embodiment of the present application includes a detection probe module 101 (detection probe detector) and a voltage drive module 102 (voltage driver buffer). The detection probe is an impedance detection probe, including a voltage divider resistor and a DC isolation capacitor, and the biological impedance value is measured using a series resistor based on the voltage division principle; the detection circuit uses an adjustable voltage divider resistor and an adjustable DC isolation capacitor, and the measurable resistance value ranges from several kΩ to several MΩ; the voltage drive module 102 maintains the measured voltage value and sends it to the analog-to-digital conversion circuit to obtain a digital value to participate in the system feedback control.

In some embodiments, the voltage attenuation capacitor includes a first capacitor Cs1 and a second capacitor Cs2 connected in parallel, and a first adjustable capacitor Cp1 and a second adjustable capacitor Cp2 arranged between the output end of the first capacitor Cs1 and the output end of the second capacitor Cs2; the control output switch includes two, and the input ends of the two control output switches (the fourth switch S4 and the fifth switch S5) are respectively connected to the output end of the first capacitor Cs1 and the output end of the second capacitor Cs2, and the first adjustable capacitor Cp1 and the second adjustable capacitor Cp2 are respectively connected to the output end of the first capacitor Cs1 and the output end of the second capacitor Cs2. Cp2 is located between the input ends of the two control output switches, that is, the first adjustable capacitor Cp1 and the second adjustable capacitor Cp2 connected in series are located between the input ends of the fourth switch S4 and the fifth switch S5.

In some embodiments, the control switch of the voltage divider unit 1011 includes a first switch S1, a second switch S2 and a third switch S3, the input end of the first switch S1 is connected to the output end of the stimulation voltage Vs, and the output end of the first switch S1 is connected to the nanowire electrode; the second switch S2 and the third switch S3 are respectively connected in parallel at both ends of the first switch S1, and the adjustable voltage divider resistor Rs is set between the output end of the second switch S2 and the output end of the third switch S3.

In some embodiments, the first switch S1 , the second switch S2 , and the third switch S3 are all detection mode control switches.

In the present application, the bioimpedance detection circuit has a detection range of 5k-2Mohm according to the design requirements, and the absolute accuracy requirement is not high. A fully integrated solution can be adopted, and the structure of the detection circuit is shown in Figure 2. The structure of the detection band circuit includes a detection probe module 101 and a voltage driving module 102. The detection probe module 101 includes a detection mode control switch (a first switch S1, a second switch S2, and a third switch S3), an adjustable voltage divider resistor Rs, a voltage attenuation capacitor Cs and Cp, and a time-sharing control output switch (a fourth switch S4 and a fifth switch S5). The voltage driving module 102 is a voltage driver, which is used to buffer the voltage output by the detection probe module 101 to improve the voltage driving capability.

In some embodiments, the stimulation voltage is outputted by a voltage stimulator; the voltage value of the stimulation voltage is ±5V, ±9V or ±12V.

In the normal working mode, the first switch S1 is closed, the second switch S2 to the fifth switch S5 are opened, and the voltage stimulator outputs a stable configurable voltage value of ±5, ±9, ±12 multiple voltage values. The stimulation waveform is shown in Figure 3, where V represents the adjustable constant voltage stimulation voltage value. Usually, the parasitic impedance of the first switch S1 is usually on the order of 10 ohms, which is much smaller than the impedance of the nanowire electrode, and its influence can be ignored. In the impedance test mode, the first switch S1 is opened, the second switch S2 and the second switch S3 are closed, and the adjustable voltage divider resistor Rs is connected to the path of the stimulation current. At this time, the adjustable voltage divider resistor Rs divides the voltage with the electrode, and a voltage drop is generated at node A and node B. The adjustable voltage divider resistor Rs is designed to be adjustable in multiple gears to increase the resistance measurement range.

In some embodiments, the resistance of the adjustable voltage divider resistor Rs is 10k, 100k or 1M according to the impedance measurement range.

By closing the control switch S4 or S5 respectively, the voltage amplitudes _VA and _VB at the A and B nodes can be obtained respectively. The voltages at the A and B nodes are reduced to within the input voltage range of the voltage driving module 102 by capacitor voltage division.

In some embodiments, the two nodes where a voltage drop occurs at both ends of the adjustable voltage-dividing resistor are respectively recorded as node A and node B; through the voltage-dividing effect of the voltage attenuation capacitor, the voltages at node A and node B are respectively attenuated to within the input voltage range of the voltage driving module, and the nodes after voltage reduction are respectively recorded as node A' and node B'.

It should be noted that, as shown in FIG2 , node A is located at the connection between the output end of the second switch S2 and the adjustable voltage-dividing resistor Rs, and node B is located at the connection between the output end of the third switch S3 and the adjustable voltage-dividing resistor Rs. Node A' is located at the connection between the output end of the first capacitor (capacitor Cs1 at node A) and the first adjustable capacitor Cp1, and node B' is located at the connection between the output end of the second capacitor (capacitor Cs2 at node B) and the second adjustable capacitor Cp2.

When the voltage attenuation coefficient is a certain value, assuming the voltage attenuation coefficient is M, the resistance of the nanowire resistor is obtained by formula (1):

It can be seen from formula (1) that when the circuit capacitance is matched and the attenuation coefficient is equal, the resistance of the nanowire is independent of the attenuation coefficient.

In some embodiments, the attenuation voltage value is set according to the voltage value of the stimulation voltage, and the attenuated voltage value is within the input voltage range of the voltage driving module 102 through capacitor voltage division. For example, two levels of attenuation voltage values (5 times and 10 times) can be designed to ensure that the attenuation result is just within the input voltage range of the voltage driving module 102. For the adjustable capacitor design, a switch series capacitor structure is selected, but at the same time, the switch brings parasitic resistance, as shown in Figure 4, which affects the accuracy of voltage division. The present application has a voltage division point in the voltage attenuation path between the first capacitor C1 and the first adjustable capacitor C2, denoted as V _x , and the expression of the voltage division point s domain is shown in formula (2):

Considering the influence of the parasitic resistance of the switch and considering that the switch resistance is a non-constant value, the present application adopts the method shown in FIG5 to eliminate the influence of the switch resistance. The parasitic resistance of the switch is added between the first capacitor C1 and the voltage dividing point Vx to offset the influence of the switch resistance in FIG4. The expression is as shown in formula (3):

Wherein, _Vx represents the voltage at the voltage dividing point, _Vs represents the voltage value of the stimulation voltage, _C1 represents the first capacitor, _C2 represents the first adjustable capacitor, _R1 represents the added parasitic resistance of the switch, and _R2 represents the parasitic resistance of the switch.

It should be noted that, here, C1 in FIG. 4 and FIG. 5 corresponds to the first capacitor Cs1 in FIG. 2, and C2 in FIG. 4 and FIG. 5 corresponds to The first adjustable capacitor Cp1 in FIG2 corresponds to the first adjustable capacitor Cp1 in FIG2. When R ₁ /R ₂ =C ₂ /C ₁ , the parasitic resistance effect can be offset. The expression of the resistance of the nanowire to be measured can still use formula (1).

In some embodiments, the input voltage range of the voltage driving module 102 is 0.6V to 1.2V. For example, the input voltage range of the voltage driving module 102 may be 0.6V, 0.8V, 1.0V or 1.2V.

The stimulus voltage works in the high voltage domain of ±12V, while the voltage driving module 102 (buffer) and subsequent circuits work in the low voltage domain. In this design, the power supply voltage is 1.8V. It should be noted that the input voltage of the voltage driving module 102 should be less than the power supply voltage. By using a MOM capacitor with a withstand voltage of 60V, the signal is attenuated by 10 times. In this way, the buffer can process the signal within the normal voltage range. The design of the buffer uses an operational amplifier with a unit gain connection. The performance indicators of the amplifier are: 1) DC gain>90dB, reducing errors; 2) Input impedance>10Mohm reduces interference with measurement accuracy; 3) Input range 0~1.2V, adapting to the detector output. A two-stage operational amplifier and a folded cascode+miller compensation structure are used to meet the above index requirements.

An embodiment of the present application further provides a retinal prosthesis-specific chip, comprising the nanowire electrode impedance detection circuit of the retinal prosthesis-specific chip described in any of the above embodiments.

The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip provided in the present application, on the one hand, is a bio-impedance detection circuit that can be integrated on the retinal prosthesis dedicated chip, and the circuit can measure a range from 5kohm to 20Mohm, the measurement range becomes larger, and the relative accuracy becomes smaller as the resistance value to be measured becomes larger (it is more sensitive to small bio-impedance values); on the other hand, the circuit structure can be applied to voltage stimulation, and compared with the previous retinal project impedance detection circuit, an attenuation capacitor structure suitable for multi-level voltage domains is added.

The present invention has been verified by simulation. The simulation circuit is shown in FIG6. A 0-12V sine wave is used as the input excitation, and a simulation waveform as shown in FIG7 can be obtained. It is observed that the voltage value of node B decays according to the design index. Although there is a 0.4V DC voltage value (caused by the physical characteristics of the switch), the error can be eliminated by subtracting the voltages of node A and node B in a differential manner. From the simulation results, the circuit design meets the requirements of nanowire bioimpedance detection.

Based on the above technical scheme, the embodiment of the present application provides a nanowire electrode impedance detection circuit and chip for a retinal prosthesis dedicated chip, the detection circuit includes a detection probe module 101 and a voltage driving module 102; the input end of the detection probe module 101 is connected to the output end of the stimulation voltage, the output end of the detection probe module 101 is connected to the input end of the voltage driving module, and the output end of the voltage driving module 102 is connected to the input end of the analog-to-digital conversion circuit; the detection probe module 101 includes a voltage divider unit 1011 and a voltage attenuation unit 1012, the voltage divider unit 1011 includes an adjustable voltage divider resistor and a plurality of control switches, by controlling the switching state of the plurality of control switches, the adjustable voltage divider resistor is connected to the path of the stimulation current, so that the adjustable voltage divider resistor and the electrode divide the voltage, and a voltage drop is generated at both ends of the adjustable voltage divider resistor; the voltage attenuation unit 1012 includes a voltage attenuation capacitor and a plurality of The output switch is controlled, and the switching states of several output switches are controlled to obtain the voltages at the two nodes where the voltage drop occurs at both ends of the adjustable voltage-dividing resistor; through the voltage-dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module 102.

Those skilled in the art can understand that the above-mentioned embodiments are specific examples for implementing the present application, and in practical applications, various changes can be made to them in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present application, so the scope of protection of the present application shall be based on the scope defined in the claims.

Claims

A nanowire electrode impedance detection circuit for a retinal prosthesis dedicated chip, characterized by comprising:

A detection probe module and a voltage driving module; the input end of the detection probe module is connected to the output end of the stimulation voltage, the output end of the detection probe module is connected to the input end of the voltage driving module, and the output end of the voltage driving module is connected to the input end of the analog-to-digital conversion circuit;

The detection probe module includes a voltage dividing unit and a voltage attenuation unit. The voltage dividing unit includes an adjustable voltage dividing resistor and a plurality of control switches. By controlling the switch state of the control switch, the adjustable voltage dividing resistor is connected to the path of the stimulation current, so that the adjustable voltage dividing resistor and the electrode divide the voltage, and a voltage drop is generated at both ends of the adjustable voltage dividing resistor;

The voltage attenuation unit includes a voltage attenuation capacitor and a plurality of control output switches. By controlling the switching state of the control output switch, the voltages at the two nodes where a voltage drop occurs at both ends of the adjustable voltage-dividing resistor are obtained respectively; through the voltage-dividing effect of the voltage attenuation capacitor, the voltages at the two nodes are attenuated to within the input voltage range of the voltage driving module.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the voltage attenuation capacitor includes a first capacitor and a second capacitor connected in parallel, and a first adjustable capacitor and a second adjustable capacitor arranged between the output end of the first capacitor and the output end of the second capacitor;

The control output switches include two, the input ends of the two control output switches are respectively connected to the output end of the first capacitor and the output end of the second capacitor, and the first adjustable capacitor and the second adjustable capacitor are located between the input ends of the two control output switches.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the control switch of the voltage divider unit includes a first switch, a second switch and a third switch, the input end of the first switch is connected to the output end of the stimulation voltage, and the output end of the first switch is connected to the nanowire electrode;

The second switch and the third switch are respectively connected in parallel to two ends of the first switch, and the adjustable voltage-dividing resistor is arranged between an output end of the second switch and an output end of the third switch.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 3 is characterized in that the first switch, the second switch and the third switch are all detection mode control switches.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the two nodes generating voltage drops at both ends of the adjustable voltage divider resistor are respectively recorded as node A and node B;

Through the voltage division effect of the voltage attenuation capacitor, the voltage at the node A and the node B are respectively attenuated to within the input voltage range of the voltage driving module, and the nodes after the voltage reduction are respectively recorded as the node A' and the node B';

When the voltage attenuation coefficient is a certain value, the resistance of the nanowire resistor is obtained by formula (1):

Wherein, R electrode represents the resistance of the nanowire, R s represents the adjustable voltage divider resistance, VA represents the voltage at the node A, VB represents the voltage at the node B, VA ' represents the voltage at the node A' after voltage reduction, and VB ' represents the voltage at the node B' after voltage reduction.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 2 is characterized in that the attenuation voltage value is set according to the voltage value of the stimulation voltage, and the attenuated voltage value is made to be within the input voltage range of the voltage driving module through capacitor voltage division;

There is a voltage dividing point in the voltage attenuation path between the first capacitor and the first adjustable capacitor, which is denoted as V x . The expression of the voltage dividing point s domain is shown in formula (2):

Considering the influence of the parasitic resistance of the switch, the parasitic resistance of the switch is added between the first capacitor and the voltage dividing point, and formula (3) is obtained:

Wherein, Vx represents the voltage at the voltage dividing point, Vs represents the voltage value of the stimulation voltage, C1 represents the first capacitor, C2 represents the first adjustable capacitor, R1 represents the added switch parasitic resistance, and R2 represents the switch parasitic resistance.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the resistance of the adjustable voltage divider resistor is 10k, 100k or 1M.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the stimulation voltage is output through a voltage stimulator; the voltage value of the stimulation voltage is ±5V, ±9V or ±12V.
The nanowire electrode impedance detection circuit of the retinal prosthesis dedicated chip according to claim 1 is characterized in that the input voltage range of the voltage driving module is 0.6V to 1.2V.
A retinal prosthesis-specific chip, characterized in that it comprises a nanowire electrode impedance detection circuit of the retinal prosthesis-specific chip as described in any one of claims 1 to 9.