Sigma-Delta ADC on SOI Technology for Working at High Temperatures

Abstract

We consider the integrated circuit design and the measurement results of test crystals for the 12-bit sigma-delta analog-to-digital converter (ADC) based on 180 nm silicon-on-insulator (SOI) technology from X-FAB. The ADC processes input signals in the frequency range up to 100 kHz in the temperature range of –40…+175 °C with the supply voltage equal to 3.3 V and the modulator clock frequency equal to 10 MHz. The circuit consists of the 5-th order switched-capacitor low-pass pre-filter to limit the input signal spectrum, the cascade connection of the second order sigma-delta modulators, and the digital decimation filter to reduce the clock frequency by 48 times. The main blocks of cutoff filter and modulator are assembled according to the balanced scheme on integrators based on operational transconductance amplifiers with the unity gain bandwidth of 63 MHz. The dynamic element matching circuit is used to expand the dynamic range of converter. It reduces the level of nonlinear distortions in digital-to-analog converters in the feedback circuits of modulator. The value of the SINAD parameter is not worse than 68 dB for converting the signal with the differential amplitude equal to 500 mV at the frequency of 100 kHz.