A 0.4V 6.5nW 10b 2.5kS/s asynchronous SAR ADC

A 0.4V 6.5nW 10b 2.5kS/s SAR ADC is proposed for energy-limited applications such as wireless micro-sensor networks, biomedical, and energy harvesting systems. The ADC operates at extremely low supply voltage (0.4V) to reduce power consumption and to eliminate short-circuit current. The channel length of MOSFETs in digital block is optimized to minimize digital power consumption. Small unit capacitor and low top parasitic capacitance is obtained by the proposed capacitor structure. The simulation results show that SFDR, SNDR, ENOB are 63.8dB, 58.1dB and 9.4bit at Nyquist input frequency, respectively. The figure-of-merit (FOM) is 3.98fJ/conv-step.