16‐bit 1‐MS/s SAR ADC with foreground digital‐domain calibration

This study presents a low‐power 16‐bit 1‐MS/s successive approximation register analogue‐to‐digital converter (SAR ADC) for medical instrument applications. A foreground digital‐domain calibration method simultaneously correcting mismatch errors in capacitive digital‐to‐analogue converter (CDAC) and ‘segment error’ of split‐CDAC array is proposed. The split‐CDAC architecture combines a V cm ‐free technique in a floating CDAC scheme. The V cm ‐free technique avoids a power hungry V cm generator, and the floating CDAC scheme allows the conversion of a high‐voltage input signal with low supply voltage and without a significant attenuation of the input signal. Moreover, a modified direct‐switching SAR logic is adopted to improve the conversion speed. The prototype was fabricated in a 0.18 µm 1P6M Complementary Metal Oxide Semiconductor (CMOS) technology, and achieves 86.16 dB signal‐to‐noise and distortion ratio and an Figure of Merit (FOM) of 0.41 pJ/conversion‐step.