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Title:SHA-less pipeline ADC design with sampling clock skew calibration
Author(s):Huang, Pingli
Director of Research:Chiu, Yun
Doctoral Committee Member(s):Feng, Milton; Rosenbaum, Elyse; Wong, Martin D.F.
Department / Program:Electrical & Computer Eng
Discipline:Electrical & Computer Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Sample-and-hold amplifier (SHA)
pipelined ADC
multi-bit pipeline architecture
sampling clock skew
skew calibration.
analog-to-digital converters (ADCs)
Abstract:The power efficiency of pipeline analog-to-digital converters (ADCs) can be substantially improved by eliminating the front-end sample-and-hold amplifier (SHA). However, in a SHA-less architecture the sampling clock skew between the sub-ADC and the multiplying digital-to-analog converter (MDAC) in the pipeline first stage results in gross conversion errors at high input frequencies. This skew effect is aggravated in a SHA-less multi-bit-per-stage pipeline architecture, where the built-in redundancy is limited. Sampling clock skew is an essential problem in SHA-less pipeline ADCs that prohibits their use at high input frequency applications. In this thesis, a mostly digital background calibration technique is developed to remove the sampling clock skew in SHA-less pipeline ADCs. The skew information is extracted from the first-stage residue output with two comparators sensing out-of-range errors; a gradient-descent algorithm is used to adaptively adjust the timing of the sub-ADC to synchronize with that of the sample-and-hold (S/H) in the MDAC. A prototype 10-bit, 100-MS/s SHA-less pipeline ADC incorporating this calibration technique was designed and fabricated in 90-nm CMOS process. The prototype ADC converts from DC to the 12th Nyquist band with a 3.5-bit front-end stage. It digitizes inputs up to 610 MHz without skew errors in experiments; in contrast, the same ADC fails at 130 MHz with calibration disabled. The calibration circuits were fully integrated on chip. The ADC consumes 12.2 mW and occupies 0.26-mm2 silicon area, while the calibration circuits dissipate 0.9 mW and occupy 0.01 mm2. A 71-dB spurious-free dynamic range (SFDR) and a 55-dB signal-to-noise-and-distortion ratio (SNDR) were measured with a 20-MHz sine-wave input, and a larger than 55-dB SFDR was measured in the 10th Nyquist band.
Issue Date:2012-02-01
Rights Information:COPYRIGHT 2011 PINGLI HUANG
Date Available in IDEALS:2014-02-01
Date Deposited:2011-12

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