A 15bit 140μW scalable-bandwidth inverter-based audio ΔΣ modulator with >78dB PSRR

A discrete-time audio ΔΣ modulator for digital MEMS microphones is presented that exploits the advantage of using simple digital inverters instead of OTAs. To increase the robustness of the inverter approach and the power supply rejection of the pseudo-differential architecture, an internally generated supply is used to regulate the inverter bias point. The ΔΣ modulator features a scalable signal bandwidth up to 150kHz to also support ultrasonic frequencies for proximity sensing applications such as gesture recognition. In the 20kHz audio band, the modulator dissipates 140μW from a 1.5V supply and achieves a DR of 92.6dB, a SNDR of 87.9dB, and a THD of -102.7dB, respectively.