| 摘要 |
When a control power source voltage becomes lower than an operation guarantee voltage level, the output of a start-up circuit assumes an H-level, a NOR gate produces an output shut-off signal of an L-level, and FETs are turned off. As the control power source voltage further decreases, the output shut-off control circuit loses stability in the operation. In this case, a resistor maintains the FETs in the OFF state due to its pull-down operation. As a result, the output of the output circuit is maintained in a high-impedance state over the whole range of control power source voltages lower than the operation guarantee voltage level.
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