| 摘要 |
PROBLEM TO BE SOLVED: To provide an output signal control circuit for an electronic device that discriminates an ON/OFF of a power supply of an opposite device by detecting a bias voltage of the opposite device connected to the output signal control circuit via an external bus and controls a current at an output of its own bias voltage so as to prevent elements of an interface system circuit with respect to the external bus due to an overcurrent from being destroyed. SOLUTION: When a control signal S1 of a bias detection circuit 3a is at an 'L', a gate N4 of a PMOS 8 of an output stage of a constant voltage output circuit 2a is connected to a power supply voltage terminal VDD, the PMOS 8 is interrupted, a minimum source current is outputted from an output terminal N2 to charge up a large capacitance capacitor connected to the output terminal N2 for a prescribed time so as to prevent PMOS transistors(TRs) 5-8 at the output stage due to an overcurrent from being destroyed, a current density in excess of a current permissible value depending on a p<+> diffusion area of the PMOS of a cable drive interface circuit is not produced by a forward current of a parasitic diode of the PMOS of the cable drive interface circuit of an electronic device 1b so as to prevent PN junctions of output stage elements of the cable drive interface circuit from being destroyed.
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