A 1.2-MHz 10-bit Continuous-Time Sigma-Delta ADC Using a Time Encoding Quantizer

This paper shows the operating principle and experimental results of a new continuous-time sigma-delta modulator architecture. The proposed modulator does not require a multibit quantizer nor a mismatch-shaping digital-to-analog converter to produce a multibit noise-shaped output. Instead, its quantizer encodes the loop filter output in a binary signal using a time encoding technique similar to pulsewidth modulation. This binary signal is used to generate both the analog feedback loop signal and the digital output. A proof-of-concept chip in 0.35- {\rm \mu}{\hbox{m}} CMOS achieves 10 bits of resolution within a signal bandwidth of 1.2 MHz using a first-order modulator.