A 9-bit 100-MS/s 1.46-mW Tri-Level SAR ADC in 65 nm CMOS

Yanfei CHEN  Sanroku TSUKAMOTO  Tadahiro KURODA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E93-A   No.12   pp.2600-2608
Publication Date: 2010/12/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E93.A.2600
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on VLSI Design and CAD Algorithms)
Category: Circuit Design
Keyword: 
ADC,  successive approximation,  charge redistribution,  calibration,  low power,  

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Summary: 
A 9-bit 100-MS/s successive approximation register (SAR) ADC with low power and small area has been implemented in 65-nm CMOS technology. A tri-level charge redistribution technique is proposed to reduce DAC switching energy and settling time. By connecting bottom plates of differential capacitor arrays for charge sharing, extra reference voltage is avoided. Two reference voltages charging and discharging the capacitors are chosen to be supply voltage and ground in order to save energy and achieve a rail-to-rail input range. Split capacitor arrays with mismatch calibration are implemented for small area and small input capacitance without linearity degradation. The ADC achieves a peak SNDR of 53.1 dB and consumes 1.46 mW from a 1.2-V supply, resulting in a figure of merit (FOM) of 39 fJ/conversion-step. The total active area is 0.012 mm2 and the input capacitance is 180 fF.