Differential Capacitive Readout Circuit Using Oversampling Successive Approximation Technique

作者：Zhong, Longjie^*; Lai, Xinquan; Song, Hongjiang; Xu, Donglai

来源：IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, 2018, 65(12): 4072-4085.

DOI：10.1109/TCSI.2018.2849992

• Accelerometer
• closed-loop
• compact size
• low power
• micro-electromechanical systems (MEMS)
• noise floor
• sensor

This paper designs a close loop Sigma-Delta readout circuit for differential MEMS accelerometer. A technique named oversampling successive approximation (OSA) is employed to build basic amplifiers and integrators. This technique can largely reduce the gain error and thus low gain amplifier such as single stage amplifier is allowed to be used. As a result, the power consumption and chip area are reduced. However, the OSA-based amplifiers and integrators are vulnerable to the interference caused by charge injection and leakage current from the specific MOSFET switches. This drawback is analyzed in detail and the interference suppressing solutions are given. The OSA-based readout circuit is fabricated in a commercial 0.18 mu m BCD process. The measurement results show that the interference is reduced by 20 dB in the circuit with interference suppressing solutions compared with the circuit without interference suppressing solutions. And the noise floor is 24 mu g/rtHz. The readout circuit achieves a 0.07% gain error with a low power consumption of 0.5 mW and 9 MHz sampling rate.

• 出版日期2018-12
• 单位西安电子科技大学; 武汉轻工大学