A Continuous-Time 0-3 MASH ADC Achieving 88 dB DR With 53 MHz BW in 28 nm CMOS

We present design and measurement details for a 0-3 multi-stage noise-shaping (MASH) ADC that achieves a dynamic range of 88 dB over 53 MHz signal bandwidth. The ADC utilizes a zeroth-order front-end, i.e., a 17-level flash ADC, to perform a coarse quantization and a third-order 7-level continuous-time ΔΣ back-end to digitize the residue error of the front-end. The ADC achieves the high thermal noise power efficiency of a continuous-time feedforward ΔΣ modulator and the flat signal transfer function of a flash ADC. The test chip, implemented in a 28 nm CMOS process, clocks at 3.2 GHz. The average noise spectral density with small input signals is -167 dBFS/Hz and the dynamic range is 88 dB. The test chip ADC consumes a total power of 235 mW from triple power supplies of 0.9/1.8/-1.0 V. The thermal-noise figure-of-merit, defined as FOM = DR + 10log 10 (BW/P) is 171.6 dB.