| 摘要 |
A power supply apparatus that supplies an operating voltage to a microcomputer reliably resets the microcomputer before operation becomes unstable when an external power supply voltage decreases due to interruption. A switching regulator and series regulators are included. An externally supplied power supply voltage is stepped down to generate an intermediate voltage. The intermediate voltage is stepped down to generate an operating voltage for a microcomputer core. The intermediate voltage is stepped down to generate an operating voltage for an I/O port. When the intermediate voltage becomes lower than a reset determining voltage, the power supply apparatus outputs a reset signal to the microcomputer. When the power supply voltage decreases, the microcomputer can be reliably reset and the core can be prevented from operating erratically before the voltage becomes lower than a minimum core operating voltage.
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