A Low-Power Digital Capacitive MEMS Microphone Based on a Triple-Sampling Delta-Sigma ADC With Embedded Gain

• Published in: IEEE access Vol. 10; pp. 75323 - 75330
• Main Authors: Lee, Byunggyu, Yang, Jinho, Cho, Jun Soo, Kim, Suhwan
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: A digital capacitive MEMS microphone; Amplification; Capacitors; Charge pumps; Circuit design; delta-sigma ADC; gain-embedded ADC; low-power circuits; Microelectromechanical systems; Micromechanical devices; Microphones; read-out circuit; Sampling methods; Sensitivity; Transducers; Voltage; without PGA
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2022.3188661

A triple-sampling <inline-formula> <tex-math notation="LaTeX">\Delta \Sigma </tex-math></inline-formula> ADC can replace the programmable gain amplifier commonly used in the readout circuit for a digital capacitive MEMS microphone. The input voltage can then be multiplied by subtracting a further half-period delayed differential input and using the feedback capacitor of the DAC as a sampling capacitor. This triple-sampling technique results in a readout circuit with noise performance comparable to recent designs, but with a reduced power requirement and increased sensitivity. A MEMS microphone incorporating this readout circuit, fabricated in a <inline-formula> <tex-math notation="LaTeX">0.18~\mu \text{m} </tex-math></inline-formula> CMOS process, had an area of 0.98mm 2 , achieved an A-weighted SNR of 62.1 dBA at 94 dBSPL with 520 <inline-formula> <tex-math notation="LaTeX">\mu \text{A} </tex-math></inline-formula> current consumption, to which triple-sampling was shown to contribute 4.5 dBA.