555 Timer Control Voltage pin and it's effects on cap charge

Discussion in 'General Electronics Chat' started by JingleJoe, Aug 15, 2011.

  1. JingleJoe

    Thread Starter Member

    Jul 23, 2011
    Tonight I've been researching quite a bit but have come up with no answer to my question:
    What happens to the voltage accross the capacitor in a 555 timer astable circuit when a voltage is applied to pin 5?

    My conclusion was that the cap would charge to a higher or lower voltage than it ordinarily would.

    But I want to know more detail! I'll do some experiments of my own if I have to but you haven't seen my workbench, I want to clear it up before I start building more things.

    How does the voltage applied to the control voltage pin affect the capacitor charge? graphs would help :) I love graphs.

    Additionally I feel I should mention that I know the cap ordinarily exhibits an almost triangular wave between 1/3 and 2/3 supply voltage (I also think of this as p-p = 1/3Vs, biased to half Vs)
  2. bertus


    Apr 5, 2008

    Take a look at the pages 13 and 14 of the attached datasheet from Texas Instruments.

  3. JingleJoe

    Thread Starter Member

    Jul 23, 2011
    oh that explains alot, thankyou :)
    It's biasing changes and the peak to peak voltage.