A 10.31 ENOB 3.125MHz BW fully passive 2nd-order noise-shaping SAR ADC for low cost IoT sensor networks

Abstract

This paper presents a fully passive 2nd-order noise-shaping successive approximation register (SAR) analog-to-digital converter (ADC) designed specifically for low-power and low-cost Internet of Things (IoT) applications. By optimizing the coefficients, a substantial 24 dB in-band quantization noise suppression is achieved. To further reduce power consumption and the total unit capacitor count, a hybrid switching procedure and optimal logic are utilized. The measurement result shows that this design achieves an effective number of 10.31 bits over a 3.125 MHz signal bandwidth. At a power supply of 1.8 V, the power consumption is measured to be 728 𝜇W with a sampling rate of 50 MS/s. Fabricated in 180-nm CMOS technology, the ADC core occupies an area of 0.117 mm 2 . The Schrier figure-of-merit (FoM) of 160.13 dB is obtained.

A 200kHz-bandwidth 101dB SNDR noise-shaping SAR ADC with NTF strengthening method

“…One way is to use a conventional closed-loop OTA [3,4,5,6]. Another way is to use a passive filter [7,8,9,10,11]. The active approach can achieve a sharp NTF, but it consumes static power and does not scale easily.…”