A 74-dB Dynamic-Range 625-kHz Bandwidth Second-Order Noise-Shaping SAR ADC Utilizing a Temperature-Compensated Dynamic Amplifier and a Digital Mismatch Calibration

Abstract

This paper presents the design of a 2nd-order Noise-Shaping (NS) Successive-Approximation-Register (SAR) Analog-to-Digital Converter (ADC) employing a cascade of temperature-compensated dynamic amplifier and a ring amplifier in the feedback path to realize a low-power/low-noise loop filter that is robust to temperature variation. A new mismatch calibration technique optimized for a noise-shaping SAR ADC is also presented to overcome the challenge of finding correct digital bit weights for NS SAR ADCs. Fabricated in 65 nm Complementary Metal-Oxide-Semiconductor (CMOS) process, the prototype ADC demonstrates a peak Signal-to-Noise-and-Distortion Ratio (SNDR) of 71.35 dB and a dynamic range of 74 dB with a signal bandwidth of 625 kHz. Over 80-degree of the temperature range, the ADC exhibits only 2 dB drop in SNDR thanks to the temperature-compensated dynamic amplifier. With a total power consumption of $130~\mu \text{W}$ , the ADC achieves Walden Figure-of-Merit (FoM) of FoM $_{\text {W}}= 34.4$ fJ and Schreier FoM of FoM $_{\text {S,DR}}=171$ dB, respectively.

Keywords

• Successive approximation resister (SAR)
• digital domain calibration
• noise shaping (NS)
• dynamic amplifier
• ring amplifier
• mismatch calibration