RESETTING CIRCUIT WITH BACKUP POWER SOURCE

摘要

PURPOSE:To reduce variance due to parts and temperature and improve reliability by using a negative power source for a resetting circuit with a backup power source, and composing an off circuit of respectively two diodes and capacitors. CONSTITUTION:The plus power input terminal 5 of the resetting circuit with the backup power source is connected to a backup output terminal 3 through a diode D1, and the terminal 3 is grounded through the series circuit of a capacitor C1 and a resistance R1. Further, the input terminal 5 is connected to the connection point A amount a resistance R6 connected to a minus power input terminal 9 and diodes D2 and D3. The off circuits composed of those diodes D2 and D3 are connected together reversely between the base of a transistor Q1 and the ground. Consequently, when the capacitor C1 is charged sufficiently, a CPU is supplied with electric power through the resistance R1 in case of a power failure. If the capacitor C1 is not held charged sufficiently after recover from the power failure, resetting 4 is performed.