CMOS Mixed Signal SOC for High Precision Current Sensing

Abstract

This work proposes a new switched capacitor wide dynamic-range low-power signal conditioning circuit for low-side current sensing applications like battery monitoring in automobiles[5]. The switched capacitor implementation obviates the need for explicit level-shifting circuit while enabling rail-to-rail input common mode. The closed loop SC-PGA architecture is very robust to gain drift due to temperature and supply voltage variation. The design incorporates correlated double sampling technique to overcome offset and flicker noise. A bootstrapped sub-threshold leakage suppression switch for switched capacitor (SC) circuits that operate from a single supply voltage and acquire analog input that have zero common mode is designed to achieve better performance in all PVT conditions. The proposed switch gives best combination of linearity, leakage and swing. It improves the linearity of switched capacitor circuits, when compared to the existing leakage suppression switches. This technique will achieve a dynamic range of more than 96 dB across all corners.The analog-to-digital converter used in this design is a multi-bit second order -ADC. The circuit is implemented in AMS 0.35 and#956;m CMOS process with 3.3 V supply. The measurement results shows that the overall system, i.e., PGA and -ADC, achieves a dynamic range in excess of 60 dB while consuming 2 mA in all the required gain settings. The --ADC alone achieves a dynamic range in excess of 84 dB. newline