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.

中文翻译：

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采用SOI技术的Sigma-Delta ADC可在高温下工作

摘要

我们考虑基于X-FAB的180 nm绝缘体上硅（SOI）技术的12位sigma-delta模数转换器（ADC）的集成电路设计和测试晶体的测量结果。ADC在–40…+ 175°C的温度范围内处理高达100 kHz频率范围内的输入信号，电源电压等于3.3 V，调制器时钟频率等于10 MHz。该电路由用于限制输入信号频谱的5阶开关电容器低通前置滤波器，二阶sigma-delta调制器的级联连接以及将时钟频率降低48倍的数字抽取滤波器组成。截止滤波器和调制器的主要模块是根据平衡积分方案组装的，该积分方案基于具有63 MHz单位增益带宽的运算跨导放大器。动态元件匹配电路用于扩展转换器的动态范围。它降低了调制器反馈电路中数模转换器中的非线性失真水平。对于在100 kHz频率下转换差分幅度等于500 mV的信号，SINAD参数的值不小于68 dB。