RESET CIRCUIT AND MICROCOMPUTER-MOUNTED DEVICE

PROBLEM TO BE SOLVED: To reset a microcomputer even when power supply to a microcomputer-mounted device is interrupted.SOLUTION: In an electronic control device 1, a power supply circuit 19 generates a power supply voltage (hereinafter referred to as VS) for microcomputer 21 from a battery voltage (Vbat) to a power supply input line 17. A reset circuit 2 includes: a resistance 27 for pulling up a reset terminal 25 of the microcomputer 21 to the VS; a circuit 29 for performing power-on reset to the microcomputer 21 when the VS rises; a MOSFET 51 that is turned on to supply the VS to the upstream of the resistance 27; a resistance 52 connected between the upstream of the resistance and the ground; and a resistance 53 for driving connected between the power supply input line 17 and the gate of the MOSFET 51. Then, when the battery voltage to the power supply input line 17 is interrupted, the MOSFET 51 is turned off, and the reset terminal 25 is turned into 0 V by the resistance 52 before the VS is lowered to the minimum operating voltage Vmin of the microcomputer 21.