| 摘要 |
PROBLEM TO BE SOLVED: To prolong memory backup time in a simple configuration. SOLUTION: A 3 V power source is used for operating a memory 1 and a 5 V power source is used for charging a capacitor 4 for memory backup. Since a resistor 3 for limiting current is provided, a current is supplied only from the 3 V power source to the memory 1 when operating the memory 1. At the time of backup, a backup current is supplied by electric charges stored in the capacitor 4 in place of the 3 V power source.
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