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Title An Efficient Digital-domain Calibration Technique for SAR ADCs using a Bridge Capacitor
Authors Jae-Sik Yoon(Jae-Sik Yoon) ; Jintae Kim(Jintae Kim)
Page pp.79-86
ISSN 1598-1657
Keywords Split-CDAC ; digital calibration ; successive approximation register ADC ; least-squares optimization ; sine wave fitting
Abstract This paper presents an efficient digitaldomain calibration method that can correct static nonlinearity in SAR ADCs using a split capacitor DAC (CDAC). A design approach to embed redundancy in CDAC transfer characteristic by using oversized bridge capacitor is described. Finding optimal digital weights for raw ADC outputs is cast as a least-squares minimization, which can be solved as a convex optimization problem. Solving the optimization problem yields optimal digital weights that minimize the errors arising from bridge capacitor parasitics and unit capacitor mismatch in a globally optimal way. Behavioral simulations as well as the measured results using a prototype 0.7 V 5 MS/s split CDAC SAR ADC in 65 nm CMOS verify the feasibility of the proposed calibration. The presented calibration requires the fewest number of ADC outputs to obtain optimal digital weights when compared to other states-of-the-arts.