A 72 dB-DR 465 MHz-BW Continuous-Time 1-2 MASH ADC in 28 nm CMOS

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This paper presents a continuous-time (CT) multi-stage noise-shaping (MASH) ADC in 28 nm CMOS. The MASH ADC uses a first-order front-end stage to digitize the input signal and a second-order back-end stage to digitize the quantization noise of the coarse flash ADC inside the front-end. An RC lattice filter and a current-steering DAC are utilized to extract the front-end coarse quantization residue. The prototype MASH ADC chip built in a 28 nm CMOS process is clocked at 8 GHz with an OSR of 8.6, providing a signal bandwidth of 465 MHz. The ADC achieves a DR of 72 dB and an average small-signal NSD of −160 dBFS/Hz. The peak SNR is 68 dB and the peak SNDR is 67 dB. The IM3 is −88 dBFS with two −9 dBFS tones at the band edge. The ADC consumes 890 mW of power from +1.8/1.0/-1.0 V supplies and achieves a thermal noise FOM of 159 dB.