Electricity: measuring and testing – Plural – automatically sequential tests
Patent
1987-08-05
1989-08-29
Eisenzopf, Reinhard J.
Electricity: measuring and testing
Plural, automatically sequential tests
324 73AT, 324522, 324537, G01R 3102
Patent
active
048620696
ABSTRACT:
A circuit tester (12) tests an electronic circuit (10) to determine which of a number of bus devices (16, 18, and 20) on the circuit (10) is stuck in an asserting state and is thus keeping a bus (14) at the asserted voltage level. A back-driving source (21) back-drives the bus (14) to its de-asserted level, and each of the devices (16, 18, and 20) is enabled individually in succession. When a device is enabled, a current meter (22) determines whether the bus current increases as a result. If so, the given device is not the defective device that is keeping the bus asserted. If there is no current change, the device is the defective one. A current limit is imposed on the back-driving source (16). This limit depends on the particular device being enabled; the limit is set higher than the quiescent assertion current on the bus but less than the sum of the quiescent current and the assertion-current capacity of the device being enabled. Reduced current and voltage on the bus, and thus reduced power dissipation during the enablement of a device, thereby result.
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Burns W.
Eisenzopf Reinhard J.
GenRad Inc.
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