A Single-Supply 84 dB DR Audio-Band ADC for Compact Digital Microphones

Abstract

A 20 kHz audio-band ADC with a single pair of power and ground pads is implemented for a digital electret microphone. Under the limited power/ground pad condition, the switching noise effect on the signal quality is estimated via post simulations with parasitic models. Performance degradation is minimized by time-domain noise isolation with sufficient time-spacing between the sampling edge and the output transition. The prototype ADC was implemented in a 0.18 mu m CMOS process. It operates under a minimum supply voltage of 1.6 V with total current of 420 mu A. Operating at 2.56 MHz clock frequency, it achieves 84 dB dynamic range and a 64 dB peak signal-to-(noise+distortion) ratio. The measured power supply rejection at a 100 mVpp 217 Hz square wave is -72 dB.