Overcurrent protection circuit when setting current using a package control pin

US7881031B2 · kind B2 · utility

Assignee

• Micrel, Inc. · US

Inventors

• Bernd Neumann · Radevormwald, DE
• Maik Pohland · Frankfurt, DE
• Dieter Kühnel · Frankfurt, DE

Key dates

• Filing date: Dec 7, 2007
• Grant date: Feb 1, 2011
• Expiry date: Jun 1, 2029

Classification

• Technology area (CPC G): Physics
• CPC primary: G05F1/573
• WIPO field: Control
• WIPO sector: Instruments

Abstract

An overcurrent protection circuit for a current setting circuit is disclosed herein that prevents a user-selectable current from exceeding a current limit when an incorrect current selecting component (or current selecting circuit) is connected to an external control pin of a package by the user, or when the control pin is inadvertently grounded. The protection circuit senses a current (A1*Iset) mirrored from the user-set current (Iset). If the mirrored current is above a threshold, the protection circuit limits the Iset current to be at or below a current limit level. In one embodiment, the protection circuit comprises a transistor that turns on when the mirrored current exceeds a threshold, and the transistor shunts control current from a series transistor generating the user-set current Iset.