A Reference Voltage Circuit Applied in High Precision Delta-Sigma ADC

Abstract

A novel reference voltage circuit design which is applied in high-precision Delta-Sigma ADC is implemented. The proposed reference circuit exploits a high-gain class-AB OTA as the error amplifier, which improves the transient response characteristics, ensures loop stability, and does not increase additional power consumption. The design and simulation of the proposed reference voltage circuit are fabricated by SMIC.18 CMOS technology. The simulation results manifest that the temperature coefficient of the bandgap reference is 6.825 ppm/°C in the temperature range from -40°C to 125°C. The transient response of the proposed reference circuit takes about 13 ns to reach the precision demanded by the reference voltage. The Σ-Δ modulator with the designed reference voltage circuit applied has an effective number of bits (ENOB) of 18.1 bits, a signal-to-noise-ratio (SNR) of 111.2 dB, and a signal-to-noise-plus-distortion (SNDR) of 110.9 dB at 1MHz sampling frequency and 625 Hz input signal.