| 摘要 |
<p>PURPOSE:To generate assuredly a reset pulse although a power supply is cut off or reapplied with any timing, by utilizing a general-purpose timer IC. CONSTITUTION:The voltage of a threshold terminal (d) rises up with a time constant decided by the products of the time constant values of a resistance 23 and a capacitor 24 after a power supply 20 is applied. If the power supply voltage is set at VCC, the reference voltage at the inside of a timer IC25 is set at (2/3XVCC). Then the 1st voltage comparator 11 is inverted when (threshold voltage)>=(2/3XVCC) is satisfied. A reset input is applied to a flip-flop 13, and the output Q of the flip-flop 13 is set at 1. Then the output of a terminal (g) is also set at 1. Furthermore, the output Q is set at 1 to make a transistor TR16 conduct since terminals (d) and (h) are connected in common. At the same time, the electric charge stored in a capacitor 24 is discharged instantaneously through the TR16. Thus the voltage between both ends of the capacitor 24 is kept approximately at 0V.</p> |
