| 摘要 |
<p>PURPOSE:To prolong the life of a backup battery by providing a circuit which prevents a current supplied from the backup battery from flowing into an input terminal. CONSTITUTION:Tri-state buffer circuits B1-B3 are respectively inserted between the input terminals 2-4 and pull up resistances R1-R3, and pull down resistance R4-R6 whose one ends are connected to the side of a ground are respectively inserted between the tri-state buffer circuits B1-B3 and the input terminals. When power block occurs on the side of an equipment in a state that the equipment is connected with an external equipment, the tri-state buffer circuits B1-B3 come to the state of high impedance since control input signal CNT show a zero level. Thus, the current does not flow from the backup battery Batt to the terminals 2-4 through the tri-state buffer circuits B1-B3, and therefore the consumption of the backup battery Batt can be prevented.</p> |
