基于共源共栅反相器的极低功耗Sigma-Delta调制器设计

Design of extremely low power sigma-delta modulator based on cascode inverter

为了满足穿戴式医疗设备中低功耗、高精度的模数转换应用需求,设计一种基于共源共栅反相器的低功耗14bit/500Hz Sigma-Delta调制器电路.在低电源电压环境下,该电路采用栅压自举开关完成了高精度的信号采样.利用共源共栅反相器替换传统Sigma-Delta调制器的跨导放大器(DTA),有效降低了电路功耗.电路采用SMIC 0.13μm 1P8M混合信号工艺实现,测试结果表明,在供电电压为0.6V、时钟频率为256kHz、信号带宽为500 Hz内,Sigma-Delta调制器输出信号最大信噪失真比为69.7dB,有效精度为11.3bit,功耗仅为5.07μW.

A 14 bit/500 Hz Sigma-Delta modulator was presented based on cascode inverter to meet the low power,high resolution application requirement of wearable medical device.In low power supply,the bootstrap switch was adopted to complete accurate signal sampling.And instead of using a transconductor operational amplifier（OTA）,the Sigma-Delta modulator was constituted with cascode inverter to reduce power consumption.The circuit was implemented in SMIC 0.13μm 1 P8 M Mixed-signal process.The measurement results show that in 0.6 Vpower supply with 500 Hz signal bandwidth and 256 kHz clock frequency,the maximum signal to noise and distortion ratio（SNDR）is 69.7 dB and the efficient number of bit（ENOB）is 11.3 bit with 5.07μW power consumption.