A low-voltage zero-crossing-based delta-sigma analog-to-digital converter

Abstract

A zero-crossing-based (ZCB) switched-capacitor technique is presented for operation under low power supply voltages without gate boosting. Voltage ramp generators maintain common-mode level at each integrator output. Correlated level-shifting is used to increase the effective output impedance of gated current sources. The technique was used to design a single-bit 4th-order delta-sigma analog-to-digital converter for audio applications. The prototype ADC was implemented in 0.13 [mu]m CMOS and achieves 11.9 ENOB for 60 kHz input bandwidth while dissipating 1.2 mW power.