A 24 nW 10-bit 10 kS/s ultra-low-power SAR ADC for biomedical devices

Abstract

This paper proposed an ultra-low-power successive approximation register analog to digital converter (ADC) for medical implant devices. To reduce power consumption, the novel techniques presented in this paper are a tri-state capacitor unit, a novel switch scheme, and a new low static power comparator. Tri-state capacitor unit reduces down power without the use of middle voltage reference. The proposed switch scheme can complete the most-significant bit 3-bit conversion without any power consumption. The offset of the low static power comparator is only optimized by physical design. This ADC is fabricated in a 110 nm 1P5M CMOS process. The reference voltage of DAC is 1 V, and the supply voltage of comparator and digital logic is 1.5 V. At 10 kS/s sampling rate, the signal to noise and distortion ratio (SNDR) is 57.57 dB and power consumption is 24 nW.