A 6-b 875-MS/s SAR ADC with charge-pump based pipelined background metastability calibration

Metastability in successive-approximation register analogue-to-digital converters (ADCs) degrades the ADC's signal-to-noise and distortion ratio and causes error propagation through the digital equalizers of ADC-based receivers. To mitigate these issues, a charge-pump-based successive-approximation register metastability calibration method is proposed. This approach operates independently of a fixed voltage or time reference. The calibration process is executed in the background with pipelining, requiring minimal additional power. Comprehensive testing shows that the proposed calibration consistently enhances ADC SNDR and reduces the code error rate across a wide range of sampling rates.