Importance

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Abstract

An apparatus for diagnosing the operation of a plurality of output transistor drivers includes a plurality of detection transistors, a reference resistor and a voltage detector. Each detection resistor is coupled from a collector of one output transistor driver to a common node. The reference resistor is coupled between the common node and a ground potential. The voltage detector measures voltage across the reference resistor to determine the existence of an improperly functioning transistor. The test method includes turning off all the transistor drivers, detecting the voltage, and comparing the voltage to a reference voltage to determine if any transistors are shorted. If there are no shorts, the transistors are sequentially turned on to determine if any transistors are open.

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First Claim