automatic reset

automatic reset ulse This circuit is designed to generate a reset p whenever the supply voltage is switched on and, in addition, whenever there is any substantial inter- the supply will be fully on. The "automatic reset" works as follows. The section ference "spikes" on the power supply lines. Most digital circuits (and microprocessor systems in particular) have to be reset for a certain period after hed on. In this the supply voltage is initially switc .mate s instance, an active low reset pulse is gener which will remain logic zero for 30 ms after the supply is switched on. At the end of this duration of circuit around transistors Ti and T2 ensures that the voltage across capacitor C1 remains 0 V until the supply voltage reaches a level of 4.5 V. As soon transis- as the supply voltage reaches this value, the C1 will tors will stop conducting and capacitor gradually charge up via resistor R5. As a result, the voltage at point A will slowly drop from around 4.5 V to 0 V , causing ...