POWER SUPPLY CONTROL DEVICE

摘要

PURPOSE:To prevent the generation of unstable operation in the operating state of a central processing unit (CPU) by turning a power supply control circuit to a backup state after surely ending initial resetting operation and surely setting up the CPU and its peripheral devices to backup states. CONSTITUTION:When the CPU 20, a RAM 30, a ROM 40 and peripheral circuits are mounted in a vehicle and connected to a car battery 10, voltage VDD outputted from the battery 10 is impressed to the CPU 20 through the 1st regulator 11. Then an RST detecting circuit 42 detects whether the voltage VDD is potential capable of operating the CPU 20 or not, and when the potential disables stable operation, outputs an 'L' level RST signal. When the stable operation is possible, the signal RST is turned to the 'H' level to start the CPU 20. In this case, the output of the circuit 42 is outputted also to a Shmitt circuit 43, the preceding 'L' level signal is stopped, the 'H' level signal is delayed by a delay circuit 44, and the delayed signal is outputted to an OR circuit 45. Then, a switch 12 is turned on by the output of the circuit 45 to impress a prescribed voltage to the ROM 40 and the peripheral circuits.