A nanowatt noise-shaping SAR ADC for passive wireless sensor node application

Abstract

This paper presents a novel first-order noise-shaping successive approximation register (SAR) analog-to-digital converter (ADC) for passive wireless sensor node application. To decrease dynamic power consumption, one-side switching instead (OSSI) method and higher-bit switching instead (HBSI) method are adopted in our proposed noise-shaping architecture. Dynamic SAR logic and dynamic comparator are used to further reduce power consumption. In addition, a low supply voltage is applied to this ADC, which can decrease static current leakage. The proposed noise-shaping SAR ADC was fabricated in 0.18um 1P4M CMOS technology, which occupies an active area of 0.185mm². The prototype chip consumes 89nW at 25kHz sampling rate. The measurement shows 58.2dB signal to noise and distortion ratio (SNDR) can be achieved.