| 摘要 |
PURPOSE:To reduce the power consumption of an input buffer by connecting the other terminal of a pull-up means to the 1st main electrode of a transistor(TR), the 2nd main electrode of the TR to a main power supply and a control electrode to a backup power supply in a device provided with the backup power supply and the main power supply. CONSTITUTION:With SW1-SW3 opened, the input terminal of input buffers 5-5'' is pulled up to an H level by resistors 1-1'. With SW1-SW3 closed, the level of the input terminal of the input buffers 5-5'' goes to L. Then an N-channel FET 8 is turned on via level shifters 16-16'' and an OR circuit, a TR 11 is turned on and power is supplied to a CPU 13 and a signal processing system 14 or the like. Since the power is supplied also to the collector of a TR 2, the current flowing to the resistors 1-1' is afterwards supplied from a main power supply VMAIN. Thus, the consumption of the backup power supply VBAK is prevented and a lithium battery with high energy density is used as the backup battery.
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