A 100-nW 9.1-ENOB 20-kS/s SAR ADC for portable pulse oximeter

Hokyu Lee, Sejin Park, Chaegang Lim, Chulwoo Kim

Research output: Contribution to journalArticlepeer-review

29 Citations (Scopus)


This brief presents an energy-efficient 10-bit accuracy with 20-kS/s successive approximation register analog-to-digital converter for portable pulse oximeter. A data-dependent capacitor reset (DDCR) switching scheme for the capacitive digital-to-analog converter (CDAC) to reduce the average switching energy and the number of unit capacitors is proposed and implemented. Compared with the conventional capacitor switching scheme for CDACs, the proposed DDCR switching scheme reduces the average switching energy and the total number of unit capacitors by 97% and 75%, respectively. We achieved a signal-to-noise-and-distortion ratio of 56.5 dB and a spurious-free dynamic range of 64.7 dBc at the Nyquist input frequency. The measured peak differential and integral nonlinearities are 0.44 and 0.58 least significant bit, respectively. The figure of merit is 9.1 fJ/conversion-step. The prototype, fabricated in the 0.11-μm CMOS process, occupies 0.033 mm2.

Original languageEnglish
Article number7001238
Pages (from-to)357-361
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Issue number4
Publication statusPublished - 2015 Apr 1

Bibliographical note

Publisher Copyright:
© 2004-2012 IEEE.


  • Pulse oximeter
  • U-Healthcare
  • analog-to-digital converter
  • energy efficient
  • low-power
  • successive approximation register

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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