A 1.8-V ΔΣ modulator interface for an electretmicrophone with on-chip reference

摘要

The design of a delta-sigma (ΔΣ) analog-to-digitalnconverter (ADC) for direct voltage readout of an electret microphone isnpresented. The ADC is integrated on the same chip with a bandgap voltagenreference and is designed to be packaged together with an electretnmicrophone. Having a power consumption of 1.7 mW from a supply voltagenof 1.8 V, the circuit is well suited for use in mobile applications. Thensingle-loop, single-bit, fourth-order ΔΣ ADC operates at 64ntimes oversampling for a signal bandwidth of 11 kHz. The measuredndynamic range is 80 dB and the peak signal-to-(noise+distortion) rationis 62 dB. The harmonic distortion is minimized by using an integratornwith an instrumentation amplifier-like input which directly integratesnthe 125-mV peak single-ended voltage generated by the microphone. Ancombined continuous-time/switched-capacitor design is used to minimizenpower consumption