A Single-Chip Analog-to-Digital Conversion System for Audio Codecs

摘要

A single-chip data conversion system for encapsulation with an electret microphone is presented. The system integrates a high impedance, single-ended input fourth-order ΣΔ modulator and a bandgap voltage reference. It converts the single-ended voltage generated by an electret microphone to a 1-bit digital stream with better than 10-bit linearity. The conversion resolution, limited by circuit noise, is better than 13 bits for a signal bandwidth of 11kHz. The entire system is biased from a single supply of 1.8V and consumes 1.7mW. Small area and power consumption make it fit to be placed inside microphone's metal can, thus improving the tolerance of signal processing to externally generated noise. Only four wires are needed to connect the chip from outside the can: supply, ground, clock and 1-bit data.