Accurate Sneak-Path-Controlled Readout for a Cross-Point Resistive Sensor Array

Abstract

A readout method of measuring resistances from a sensor array is proposed. As opposed to the conventional method of feedback readout, in which the crosstalk is suppressed by an op-amp, the sneak paths are controlled by switches, and a matrix equation of the circuit is derived from measured voltage. Thus, the scanning speed and power consumption of an interface circuit are not inherently deteriorated by the op-amp. The main factors affecting readout accuracy are parasitic resistance of the analog switch and quantized error of the analog-to-digital converters (ADCs). Therefore, calibration of switch resistance is also proposed to maintain readout accuracy by additional ADCs. To evaluate the proposed readout system, “sneak-path-controlled readout” (SPCR) and “accurate sneak-path-controlled readout” (ASPCR) are implemented. To verify the accuracy of the proposed readout method, the interface circuit and the calibration of switch resistance were simulated by MATLAB. The target array size was 32×32, and the sensor resistances were distributed in the same manner as real sensors. Since readout performance is also affected by the pattern of resistances, several patterns of resistance were prepared, and their results were compared. The results of the simulations show that SPCR using a 16-bit ADC can read normally distributed sensors with readout error of 0.05%. Moreover, ASPCR can handle a wider resistance distribution, and its readout error was less than 0.3% with a resistance pattern in which resistance ranges from 1.71 kΩ to 217 kΩ.