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A triple-sampling ΔΣ 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 sensitivity and noise performance comparable to recent designs, but with a reduced power requirement. A MEMS microphone incorporating this readout circuit, fabricated in a 0.18 μm CMOS process, had an area of 0.98 mm 2 , achieved an A-weighted SNR of 62.1 dBA at 94 dBSPL with 520 μA current consumption, to which triple-sampling was shown to contribute 4.5 dBA. INDEX TERMSA digital capacitive MEMS microphone, gain-embedded ADC, delta-sigma ADC, without PGA, read-out circuit, low-power circuits.

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