A Wide Dynamic-Range Low-Power Signal Conditioning Circuit for Low-Side Current Sensing Application

Abstract

This paper proposes a wide dynamic-range lowpower signal conditioning circuit for low-side current sensing application. The proposed architecture uses a double sampling technique for switched capacitor programmable gain amplifier (SC-PGA) thus enabling the PGA to work at low frequency However, the analog-to-digital converter (ADC), which digitizes the amplified signal works at high frequency to achieve high dynamic range. The double sampling technique relaxes the slewrate and settling requirement of the op amp in the PGA. 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. The analog-to-digital converter used in this design is a multi-bit second order ΔΣ-ADC [14]. The circuit is implemented in AMS 0.35 μm CMOS process with 3.3 V supply. Simulations show that the overall system, i.e., PGA and ΔΣ-ADC, achieves a dynamic range in excess of 80 dB while consuming 2 mA.