Time based architecture for high-side current sensor with integrated shunt resistor

Abstract

This paper presents a fully integrated current sensor based on an integrated shunt resistor supporting a 25V common mode input while operating at 1.2V supply voltage. It can detect a current between ±4A. It uses a novel time based architecture to increase sensor accuracy over temperature, mechanical stress and lifetime. This architecture is based on the integration of a replica of the current to sense using a switched capacitor integrator with reset working with a very accurate clock signal. With this technique sensor’s gain is not sensitive to temperature variation, mechanical stress or lifetime variation of the shunt resistor. On the other hands, its accuracy is limited only by a capacitor and the clock period variation. Their variation are much smaller than the ones of a resistor. The overall gain of this architecture achieves a precision of 1/1000 over temperature variation.