Built-in self-calibration and digital-trim technique for 14-bit SAR ADCs Achieving ±1 LSB INL

Shankar Thirunakkarasu, Bertan Bakkaloglu

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Several state-of-the-art monitoring and control systems, such as dc motor controllers, power line monitoring and protection systems, instrumentation systems, and battery monitors, require direct digitization of high-voltage (HV) input signals. Analog-to-digital converters (ADCs) that can digitize HV signals require high linearity and low-voltage coefficient capacitors. A built-in self-calibration and digital-trim algorithm correcting static mismatches in capacitive digital-to-analog converter (DAC) used in successive approximation register analog-to-digital converters (SAR ADCs) is proposed. The algorithm uses a dynamic error correction (DEC) capacitor to cancel the static errors occurring in each capacitor of the array as the first step upon power-up and eliminates the need for an extra calibration DAC. Self-trimming is performed digitally during normal ADC operation. The algorithm is implemented on a 14-bit HV input range SAR ADC with integrated DEC capacitors. The IC is fabricated in 0.6-μm HV-compliant CMOS process, accepting up to 24Vpp differential input signal. The proposed approach achieves 73.32-dB signal-to-noise and distortion ratio, which is an improvement of 12.03 dB after self-calibration at 400-kS/s sampling rate, consuming 90 mW from a ±15 V supply. The calibration circuitry occupies 28% of the capacitor DAC and consumes <15 mW during operation. Measurement results show that this algorithm reduces integral nonlinearity from as high as 7 LSBs down to 1 LSB, and it works even in the presence of larger mismatches exceeding 260 LSBs. Similarly, it reduces differential nonlinearity errors from 10 LSBs down to 1 LSB. The ADC occupies an active area of 9.76 mm2.

Original languageEnglish (US)
Article number6820772
Pages (from-to)916-925
Number of pages10
JournalIEEE Transactions on Very Large Scale Integration (VLSI) Systems
Volume23
Issue number5
DOIs
StatePublished - May 1 2015

Keywords

  • Analog-to-digital (A/D) conversion
  • digital trimming
  • mismatch correction
  • self-calibration.

ASJC Scopus subject areas

  • Software
  • Hardware and Architecture
  • Electrical and Electronic Engineering

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