An ultra-low power successive approximation A/D converter with time-domain comparator

This paper presents an ultra-low power successive approximation analog-to-digital converter. An improved implementation of the binary weighted capacitors array and a novel comparator that operates in the time instead of the voltage domain are effective and power efficient. The circuit, fabricated in a conventional 0.18-mu m CMOS technology, achieves a sampling rate of 100 kS/s and an effective number of bit of 9.4. Using a 1-V supply voltage, the achieved power consumption is 3.8 mu W, leading to a Figure of Merit as low as 56 fJ/conversion-level.