AN 8-B 85-MS/S PARALLEL PIPELINE A/D CONVERTER IN 1-MU-M CMOS

A new architecture consisting of a time-interleaved array of pipelined analog-to-digital converters (ADC's) is presented. A prototype has been designed consisting of four switched-capacitor (S/C) multistage pipelined ADC's in parallel. Hardware cost is minimized by sharing resistor strings, bias circuitry, and clock generation circuitry over the array. Digital error correction is employed to ease comparator accuracy requirements. Techniques are employed to minimize the effect of mismatches across the array. A key circuit issue is the design of a high-speed sample-and-hold (S/H) amplifier: a fully differential, mostly NMOS, non-folded-cascode op-amp topology is used. An experimental chip was implemented in 1-mum CMOS and 8-b resolution at a sample rate of 85 megasamples per second (MS/s) was obtained. Signal-to-noise plus distortion (S/(N + D)) was 41 dB for an input sinusoid of 40 MHz.