| 摘要 |
<p>PURPOSE:To prevent the runaway at a voltge restoration time by making a reset voltage lower than a threshold voltage before a microcomputer is made inactive when an external power source voltage is reduced in a power supply circuit fitted with a reset circuit. CONSTITUTION:When the voltage of an external power source 6 is reduced, an external power source voltage Vx at a point A is reduced, and the voltage at a point D is reduced by discharge of a capacitor C5, and a capacitor C is discharged for the purpose of charging the capacitor C5 through a diode D2 and a resistance R1 thereafter, and therefore, a rest voltage Vre at a point C starts reduction and reaches a threshold volage Vres after a certain time. Meanwhile, a power source voltage VCC at a point B is not reduced yet but starts reduction after a while and reaches an operation compensating voltage level VCC1 and is reduced furthermore. The runaway is prevented when the power source voltage VCC is restored to a prescribed voltage at any point of time from the state where it is lower than the operation compensating voltage level VCC1.</p> |
