A 0.0058mm2 7.0 ENOB 24MS/s 17fJ/conv. threshold configuring SAR ADC with source voltage shifting and interpolation technique

摘要

An extremely low power and area efficient threshold configuring ADC (TC-ADC) is proposed. The threshold configuring comparator (TCC) performs a binary search and only 1b-DAC is required. 5b conversion is carried out by TCC with source voltage shifting technique. Additional 2b resolution is achieved by the proposed threshold interpolation (TI) technique with only 15% power overhead. Prototype ADC in 40nm CMOS occupies a core area of only 0.0038mm2 and when calibration circuit included, 0.0058 mm2. With a supply voltage of 0.7V, the ADC achieves 7.0 ENOB with 24MS/s. Peak FoM of 9.8fJ/conv. is obtained at 0.5V supply, which is over 15x improvement compared with conventional TC-ADC.