Report on Latchup Rules for Designs with Reverse Body Bias (RBB)

  • Authors:
    Elyse Rosenbaum (UIUC), Yang Xiu (UIUC)
    Publication ID:
    Publication Type:
    Deliverable Report
    Received Date:
    Last Edit Date:
    1836.141 (University of Illinois/Urbana-Champaign)

Research Report Highlight

TxACE researchers at UIUC investigate latchup conditions on circuits that utilize reverse body bias. Measurement results from a testchip are presented and suggested guidelines are given.


This report focuses on latchup that results from the inadvertent triggering of a parasitic PNPN inherent to CMOS logic circuits. One must give special attention to latchup avoidance during the design of a CMOS IC that utilizes Reverse Body Bias (RBB). First, the resistance from the base region of the parasitic PNP [NPN] to the N-well [P-well] bias generator may be large, which will tend to lower the latchup trigger current. Second, system-level ESD may induce differential-mode noise between the N-well bias and VDD, potentially forward-biasing the base-emitter junction of the PNP inside the parasitic PNPN. This report describes a test chip in which the ESD-induced noise between the Nwell bias voltage rail and the supply rail triggered latchup, and it suggests guidelines for reducing latchup hazards in designs with RBB.

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