| 摘要 |
PROBLEM TO BE SOLVED: To obtain an apparatus which obstructs back drive automatically by detecting the generation of a back drive and its duration. SOLUTION: A pin driver circuit in a digital driver/sensor circuit of each automatic circuit tester is provided with current sensors (Rsense, QS1, QS2, D1 and D2) and a comparing circuit 58 indicating whether a load current supplied from the driver exceeds a level set by a threshold input (CURRENT VALUE). The pin driver circuit is provided with a timer 60, whose output shows whether an output of the comparing circuit 58 is asserted all over the period exceeding a range set by a period input (TIME VALUE). When the output of the comparing circuit 58 is asserted during the period, the tester makes the driver unusable, and prevents damage to be caused by an excessive back drive period which a test formation process does not predict when the driver is not made inapplicable.
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