A ±4A high-side current sensor with 25V input CM range and 0.9% gain error from -40°C to 85°C using an analog temperature compensation technique

Abstract

This paper presents a fully integrated ±4A current sensor that supports a 25V input common-mode voltage range (CMVR) while operating from a single 1.5V supply. It consists of an on-chip metal shunt, a beyond-the-rails ADC [1] and a temperature-dependent voltage reference. The beyond-the-rails ADC facilitates high-side current sensing without the need for external resistive dividers or level shifters, thus reducing power consumption and system complexity. To compensate for the shunt's temperature dependence, the ADC employs a proportional-to-absolute-temperature (PTAT) reference voltage. Compared to digital temperature compensation schemes [2,3], this analog scheme eliminates the need for a temperature sensor, a band-gap voltage reference and calibration logic. As a result, the current sensor draws only 10.9μA and is 10x more energy efficient than [2]. Over a ±4A range, and after a one-point trim, the sensor exhibits a 0.9% (max) gain error from -40°C to 85°C and a 0.05% gain error at room temperature. The former is comparable with that of other fully-integrated current sensors [2-4], while the latter represents the state-of-the-art.