A 10-b 50-MS/s 820- μW SAR ADC With On-Chip Digital Calibration

This 10-b 50-MSamples/s SAR analog-to-digital converter (ADC) features on-chip digital calibration techniques, comparator offset cancellation, a capacitor digital-to-analog converter (CDAC) linearity calibration, and internal clock control to compensate for PVT variations. A split-CDAC reduces the exponential increase in the number of unit capacitors needed and enables the input load capacitance to be as small as the kT/C noise restriction. The prototype fabricated in 65 nm 1P7M complementary metal-oxide semiconductor with MIM capacitor achieves 56.6 dB SNDR at 50-MSamples/s, 25-MHz input frequency and consumes 820 μW from a 1.0-V supply, including the digital calibration circuits. The figure of merit was 29.7 fJ/conversion-step under the Nyquist condition. The ADC occupied an active area of 0.039 mm(2) .