A 220-MS/s 9-Bit 2X Time-Interleaved SAR ADC With a 133-fF Input Capacitance and a FOM of 37 fJ/conv in 65-nm CMOS

This brief presents a 9-bit 2X time-interleaved successive approximation (SAR) analog-to-digital converter (ADC) for high-speed applications. The proposed ADC fabricated in TSMC´s 65-nm general-purpose process occupies an area of 0.0338 mm2 and consists of two time-interleaved channels, each operating at 110 MS/s. The sampling capacitor is separated from the capacitive DAC array by performing the input and DAC reference subtraction in the current domain rather than as done traditionally in the charge domain. This allows for an extremely small input capacitance of 133 fF. The measured ADC SFDR is 57 dB and the measured ENOB is 7.55 bits at Nyquist rate while using 1.55-mW power from a 1-V supply.