Time-Based Current Source: A Highly Digital Robust Current Generator for Switched Capacitor Circuits

• YOSHIOKA Kentaro

  Keio University

Abstract

The resistor variation can severely affect current reference sources, which may vary up to ±40% in scaled CMOS processes. In addition, such variations make the opamp design challenging and increase the design margin, impacting power consumption. This paper proposes a Time-Based Current Source (TBCS): a robust and process-scalable reference current source suitable for switched-capacitor (SC) circuits. We construct a delay-locked-loop (DLL) to lock the current-starved inverter with the reference clock, enabling the use of the settled current directly as a reference current. Since the load capacitors determine the delay, the generated current is decoupled from resistor values and enables a robust reference current source. The prototype TBCS fabricated in 28nm CMOS achieved a minimal area of 1200um². The current variation is suppressed to half compared to BGR based current sources, confirmed in extensive PVT variation simulations. Moreover, when used as the opamp's bias, TBCS achieves comparable opamp GBW to an ideal current source.

Journal

• IEICE Transactions on Electronics

  IEICE Transactions on Electronics E105.C (7), 324-333, 2022-07-01

  The Institute of Electronics, Information and Communication Engineers

Keywords

• current reference
• process scalable
• DLL
• switched capacitor circuits

Details

• CRID: 1390855533654382080
• NII Article ID: 130008139681
• DOI: 10.1587/transele.2021cdp0002
• ISSN: 17451353
• ISSN: 09168524
• Web Site: https://www.jstage.jst.go.jp/article/transele/E105.C/7/E105.C_2021CDP0002/_pdf
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed