一种带有DAC失配整形的高精度Sigma-Delta调制器

A high precision multi-bit sigma-delta modulator with mismatch-shaping DACs

为减小生理信号采集应用中仪表放大器的设计难度,需在低功耗、小信号带宽的前提下大幅度提高模数转换单元的精度和动态范围以作补偿。为此,面向生理信号采集应用,实现了一种带前馈结构的高精度三阶五比特Sigma-Delta调制器,其不需要复杂的OTA结构和过高的过采样率,且功耗较低,并将二阶噪声整形动态元件匹配方案应用于DAC中,以避免多比特量化造成的非线性谐波失真。该Sigma-Delta调制器采用SMIC 0.18μm CMOS标准工艺,在1 MHz的采样率,1 kHz的信号带宽内,峰值SNDR达到111 dB,动态范围达到120 dB,有效位数达到18 bit,工作电源电压为1.8 V,整体功耗为0.87 mW。

In order to reduce the difficulty of designing the amplifier of the instrument in the application of physiological signal acquisition,a higher-precision analog-to-digital conversion unit is required.This paper implements a high-precision sigma-delta modulator with feedforward structure,which does not require complex OTA structure and high oversampling rate,and has low power consumption,and a second-order noise shaping dynamic component matching scheme used in DAC to avoid nonlinear harmonic distortion caused by multi-bit quantization.The sigma-delta modulator adopts SMIC 0.18μm CMOS standard technology.At a sampling frequency of 1 MHz and a signal bandwidth of 1 kHz,the peak SNDR can reach 111 dB,the operating power supply voltage is 1.8 V,and the overall power consumption is 0.87 mW.