A Low-Power Column-Parallel ΣΔ ADC with Shared OTAs and Single-Bit-BWI Decimation Filter for CMOS Image Sensor

Zhongjie Wang, Qiyun Ma, Tongbei Yang, Zhi Lin, Amine Bermak, Fang Tang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

This article presents a low-power column-parallel analog-To-digital converter (ADC) with shared operational transconductance amplifiers (OTAs) for CMOS image sensors (CISs). Through the proposed time division multiplexing of OTAs, the power consumption of the modulator achieves a reduction of about 40%. The proposed structure alleviates the layout requirement of OTAs, enabling implementation of a high-resolution low-power image sensor in advanced CMOS technology nodes. As the coupled noise introduced by the proposed column-shared scheme is suppressed to a lower level than the inherent crosstalk of adjacent pixels, the proposed structure only contributes a negligible inter-column coupled noise from the ADCs. Moreover, a compact digital decimation filter with a single-bit-bit-wise-inversion (BWI) topology is also proposed, which can reduce chip area significantly. The prototype sensor is fabricated in a 40-nm standard CMOS technology with 256 × 256 pixel array and 256 proposed column-parallel ADCs. Each ADC occupies a core area of 4.5 {m}310 {m} , while consuming a power of 58.8 {W}. The measured differential nonlinearity (DNL) and integral nonlinearity (INL) are +0.49/-0.65 LSB and +5.1/-4.8 LSB, respectively. Measurement results show a dynamic range of 79.9 dB and an effective-number-of-bit (ENOB) of 11.4 bit. This work achieves a figure of merit (FOM) of 97.2 fJ/step.

Original languageEnglish
Pages (from-to)2979-2985
Number of pages7
JournalIEEE Transactions on Electron Devices
Volume69
Issue number6
DOIs
Publication statusPublished - 1 Jun 2022

Keywords

  • CMOS image sensor (CIS)
  • analog-To-digital converter (ADC)
  • column-parallel readout circuit
  • digital decimation filter
  • low power
  • shared operational transconductance amplifier (OTA)

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