A high precision and low power consumption switching capacitor readout circuit

Abstract

In this paper, a high precision and low power switching capacitor readout circuit for MEMS sensors is proposed. The capacitance readout circuit is realized by using the total difference separation loop structure composed of a switching capacitor charge amplifier. In order to reduce the aggravation of common-mode parasitic capacitance to the input offset error and amplifier gain error in the readout circuit, the input common-mode feedback compensation structure and oversampled successive approximation (OSA) readout technology are introduced. In addition, the circuit adopts a non-overlapping nested clock to reduce charge injection and improve output accuracy. Based on SMIC 0.18 μm CMOS technology, the circuit can recognize 0-0.2 pF capacitance signals and convert them into voltage signals, achieving good linear fitting. When the common-mode parasitic capacitance is 1-16 p, it has good resistance to common-mode parasitic capacitance, and the precision of the capacitor readout circuit is increased by 3.9%. Compared with traditional readout circuits, it has a simple structure and low power consumption.