Reset circuit for microprocessor or counter - has low resistance by=pass branch in parallel with resistor of RC element to stop resetting when set supply voltage is attained

摘要

A reset control for a microprocessor (UP) provides for a controlled start-up when the supply voltage (+24V) is switched on (S1). A resistor (R1) capacitor (C1) stage provides a time constant that controls the rate of voltage increase. A second time constant provided by a resistor (R4) and capacitor (C2) provides a slow voltage build-up on the reset line (RESET). At this point the reset is allowed to rise rapidly at a rate determined by a third time constant (R3,C2). At a threshold point reset occurs. ADVANTAGE - Controls reset following power switch-on.