Download free 555 timer pinout6/14/2023 It is positive rail connected pin which is connected to positive terminal of the power supply. It can be also used as an open collector output. The maximum allowable discharging current should be less than 50 mA otherwise the transistor may damage. It provides a discharge path for the timing capacitor through the collector of the NPN transistor, to which it is connected. The time width of this pulse should be equal or greater than 0.1uS. ![]() Typical threshold current is 0.1 mA as in the case of Reset pin. It is connected to the non inverting input of the upper comparator so that it accepts the positive going pulse to complete the timing cycle. The timing cycle is completed when voltage on this pin is equal to or greater than two-third of Vcc. When not in use, it should be connected to the ground through a 0.01uF capacitor otherwise the IC will show erratic responses Pin 6 It requires to be connected to an external DC signal to modify the timing cycle. Pin 5Ĭontrol pin – The 2/3 supply voltage point on the terminal voltage divider is brought to the control pin. The reset voltage required for this pin should be 0.7 volts at a current of 0.1mA. When this pin is grounded, the IC will stop working. It should be connected to the positive rail to work the IC properly. ![]() For logic high output, it is sourcing current with the output voltage slightly lesser than Vcc. For logic zero output, it is sinking current with voltage slightly greater than zero. It can either sink or source current which is at maximum 200mA. When the IC triggers via pin 2, the output pin goes high depending on the duration of the timing cycle. It requires a pull up connection to avoid false triggering. The triggering circuit inside the IC is too sensitive so that the IC will show false triggering due to noise in the surroundings. The current required for triggering is 0.5 uA for a period of 0.1uS.The triggering voltage maybe 1.67 V if the supply voltage is 5V and 5 V if the supply voltage is 15V. The trigger pin is connected to the Inverting input of the comparator inside the IC and accepts negative signals. It is generally low signal pin and the timer is triggered when voltage on this pin is below one third of the supply voltage. It is the Trigger pin to activate the IC’s timing cycle.
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