Volume 11, Number 23, December 2021

10-Bit, 1GS/S Time-Interleaved SAR ADC

  Authors

Shravan Kumar Donthula and Supravat Debnath, Indian Institute of Technology, Hyderabad, India

  Abstract

This paper describes the implementation of a 4-channel, 10-bit, 1 GS/s time-interleaved analog to digital converter (TI-ADC) in 65nm CMOS technology. Each channel consists of interleaved T/H and ADC array operating at 250 MS/s, with each ADC array containing 14 timeinterleaved sub-ADCs. This configuration provides high sampling rate even though each subADC works at a moderate sampling rate. We have selected 10-bit successive approximation ADC (SAR ADC) as a sub-ADC, since this architecture is most suitable for low power and medium resolution. SAR ADC works on binary search algorithm, since it resolves 1-bit at a time. The target sampling rate was 20 MS/s in this design, however the sampling rate achieved is 15 MS/s. As a result, the 10-bit SAR ADC operates at 15 MS/s with power consumption of 560 μW at 1.2 V supply and achieves SNDR of 57 dB (i.e. ENOB 9.2 bits) near nyquist rate input. The resulting Figure of Merit (FoM) is 63.5 fJ/step. The achieved DNL and INL is +0.85\-0.9 LSB and +1\-1.1 LSB respectively. The 10-bit SAR ADC occupies an active area of 300 μm × 440 μm. The functionality of single channel TI-SAR ADC has been verified by simulation with input signal frequency of 33.2 MHz and clock frequency of 250 MHz. The desired SNDR of 59.3 dB has been achieved with power consumption of 11.6 mW. This results in a FoM value of 60 fJ/step.

  Keywords

ADC, SAR, TI-ADC, LSB, MSB, T/H, SCDAC, CDAC, SFDR, SINAD, SNR, TG, EOC, D-FF, MIM, MOM, DNL, INL.