Direct-measurement provision of safe backdrive levels

US6114848A · kind A · utility

Assignee

• Genrad, Inc. · US

Inventors

• Anthony J. Suto · Sterling, US
• Robert J. Muller · Westford, US
• John D. Moniz · Fall River, US

Key dates

• Filing date: Jan 14, 1999
• Grant date: Sep 5, 2000
• Expiry date: Jan 14, 2019

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R31/31924
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Pin-driver circuitry in each of an automatic circuit tester (10)'s digital driver/sensor circuits (36) includes a current sensor (R.sub.sense, QS1, QS2, D1, and D2) and comparison circuit (58) that indicate whether the load current supplied by the driver exceeds a level set by a threshold input (CURRENT.sub.-- VALUE). The pin-driver circuitry also includes a timer (60) whose output indicates whether the comparison circuit's output has been asserted for a length of time that exceeds a limit set by a duration input (TIME.sub.-- -VALUE). When it has, the tester disables the driver and thereby prevents damage that could otherwise result from excessive backdrive durations that the test-generation process did not anticipate.