| 摘要 |
PURPOSE:To prevent the stop of watch function owing to the drop of battery voltage by detecting the drop of batery voltage from boosting voltage and inhibiting an alarm function. CONSTITUTION:When the ON resistance of an N channel transistor 4 is let to be r1, the input of an inverter 5 becomes VDD(R2 + r1)/(R1 + R2 + r1) which has voltage-divided the output VDD of a boosting circuit 3 and therefore the resistance values R1, R2 of resistances 1, 2 are beforehand so set that the relation of VDT(R2 + r1)/(R1 + R2 + r1) < VTH holds with the threshold voltage VTH of the inverter 5. Then, when the voltage VDD becomes lower than VDT, the output of a NAND gate 8 becomes ''H'' and the buzzer switch input 6 inhibits the buzzer irrespective of ''H'' of ''L''. Hence, the power consumption by the buzzer operation at the battery voltage drop may be suppressed and the stop of the watch function is prevented. |
