Split capacitor DAC mismatch calibration in successive approximation ADC

Yanfei Chen, Xiaolei Zhu, Hirotaka Tamura, Masaya Kibune, Yasumoto Tomita, Takayuki Hamada, Masato Yoshioka, Kiyoshi Ishikawa, Takeshi Takayama, Junji Ogawa, Sanroku Tsukamoto, Tadahiro Kuroda

    Research output: Contribution to journalArticlepeer-review

    10 Citations (Scopus)

    Abstract

    Charge redistribution based successive approximation (SA) analog-to-digital converter (ADC) has the advantage of power efficiency. Split capacitor digital-to-analog converter (CDAC) technique implements two sets of binary-weighted capacitor arrays connected by a bridge capacitor so as to reduce both input load capacitance and area. However, capacitor mismatches degrade ADC performance in terms of DNL and INL. In this work, a split CDAC mismatch calibration method is proposed. A bridge capacitor larger than conventional design is implemented so that a tunable capacitor can be added in parallel with the lower-weight capacitor array to compensate for mismatches. To guarantee correct CDAC calibration, comparator offset is cancelled using a digital timing control charge compensation technique. To further reduce the input load capacitance, an extra unit capacitor is added to the higher-weight capacitor array. Instead of the lower-weight capacitor array, the extra unit capacitor and the higher-weight capacitor array sample analog input signal. An 8-bit SA ADC with 4-bit + 4-bit split CDAC has been implemented in a 65 nm CMOS process. The ADC has an input capacitance of 180 fF and occupies an active area of 0.03mm2. Measured results of +0.2/-0.3LSB DNL and +0.3/-0.3LSB INL have been achieved after calibration.

    Original languageEnglish
    Pages (from-to)295-302
    Number of pages8
    JournalIEICE Transactions on Electronics
    VolumeE93-C
    Issue number3
    DOIs
    Publication statusPublished - 2010

    Keywords

    • ADC
    • Calibration
    • Comparator
    • Split capacitor DAC
    • Successive approximation

    ASJC Scopus subject areas

    • Electronic, Optical and Magnetic Materials
    • Electrical and Electronic Engineering

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