Low-Noise Chopper-Stabilized Resistive Readout Integrated Circuit with Ripple Rejection Loop

Abstract

Resistive sensors are widely used in many applications such as pressure sensors, touch screens, body composition analyzers, and acceleration sensors. Chopper stabilization is an effective solution to reduce DC offset and low-frequency flicker noises. In the demodulation stage of chopper stabilization, a high-order low-pass filter, which occupies a large area, is generally required to attenuate the up-converted DC offset and low frequency noises or "ripples". We propose a lownoise chopper-stabilized resistive readout integrated circuit (IC) with a ripple rejection loop (RRL). When the RRL operates, the modulated ripple is demodulated to the baseband. The demodulated ripple is integrated using a Miller integrator. The output of the integrator is chopped and fedback negatively to the input of the instrumentation amplifier (IA). The Miller integrator is implemented using MOS-bipolar pseudoresistors and feedback capacitors to achieve high CMRR, high DC rejection, and a small circuit size. The chip is fabricated using a 0.18-µm complementary metaloxide-semiconductor (CMOS) process with an active area of 1.8 mm 2 . The power consumption is 827 μW at 3.3 V supply. The input referred noise is measured at 0.37 μVrms in the frequency band of 1-200 Hz.