A resistance deviation-to-time interval converter for resistive sensors

A resistance deviation-to-time interval converter is presented for interfacing resistive sensors. It consists of two voltage-sources, a ramp integrator, a pair of comparator, and two logic gates. The proposed converter was designed and built on 0.35 mum CMOS process. The prototype circuit exhibits a resolution as high as 13 bits, a linearity error less than plusmn 0.1%, and environment-independent signal stability, when the output pulse is counted by 20 MHz clock signal. Moreover, the circuit complexity becomes quite simple and can be implemented in a very small space. One possible application of the proposed converter is found in a system based on any resistive-sensor like a physical contact or temperature sensor.