| 摘要 |
<p>PURPOSE:To restrain idle power consumption of a backup battery by a method wherein by operating a voltage comparison circuit by application of external electric power, high impedance is kept at the nonoperating time, and a backup current is made to flow through an objective circuit of memory or the like when voltage of the backup battery is detected. CONSTITUTION:A memory card 1 has a RAM 3, a backup battery 4 for keeping its stored data, a power change-over circuit 5 for supplying power to the RAM by changing its power to power from the outside, a reference voltage generation circuit 6 for generating reference voltage by receiving power from the outside, and a voltage comparison circuit 7 of reference voltage and backup battery voltage. A comparison terminal of the voltage comparison circuit is of a current- flowing-out type. The voltage comparison circuit is operated with external electric power and high impedance is kept at a point of nonoperating time. Then, by making the sum of an input terminal current for voltage comparison and a current from the backup battery flow to the objective circuit of memory or like as a backup current when voltage of the backup battery is detected, ineffective power consumption of the backup battery is restrained even at a point of battery voltage detection time or at a point of backup time.</p> |
