Title :
A 100-nW 9.1-ENOB 20-kS/s SAR ADC for Portable Pulse Oximeter
Author :
Hokyu Lee ; Sejin Park ; Chaegang Lim ; Chulwoo Kim
Author_Institution :
Dept. of Electr. Eng., Korea Univ., Seoul, South Korea
Abstract :
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-$mumbox{m}$ CMOS process, occupies 0.033 mm2.
Keywords :
CMOS digital integrated circuits; analogue-digital conversion; biomedical electronics; health care; DDCR switching scheme; Nyquist input frequency; SAR ADC; analog-to-digital converter; average switching energy reduction; capacitive digital-to-analog converter; conventional capacitor switching scheme; data-dependent capacitor reset; energy-efficient 10-bit accuracy; portable pulse oximeter; signal-to-noise-and-distortion ratio; spurious-free dynamic range; successive approximation register; ubiquitous healthcare; Arrays; CMOS integrated circuits; Capacitance; Capacitors; Noise; Solid state circuits; Switches; Analog-to-digital converter (ADC); Pulse oximeter; U-Healthcare; analog-to-digital converter; energy efficient; low power; low-power; pulse oximeter; successive approximation register; successive approximation register (SAR); ubiquitous healthcare (u-healthcare);
Journal_Title :
Circuits and Systems II: Express Briefs, IEEE Transactions on
DOI :
10.1109/TCSII.2014.2387680
