Power on sequence problem Help

Discussion in 'Homework Help' started by josephhsu, Dec 9, 2008.

  1. josephhsu

    Thread Starter New Member

    Dec 9, 2008
    2
    0
    I have a turn-on sequence problem for my dual power (3.3/1.2V) IC.
    1.2V must started before 3.3V. Does anyone have good idea to reach that?

    I know there are some reset ICs can do that ,but the price is first priority.

    3.3V and 1.2V comes from regulation of 5V.
    The max amp. of 3.3V and 1.2V is 400mA.
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can use a 555 timer IC and small relay to delay the 3.3 voltage to get into the circuit. Or, you can you the technique provided in the LM317 voltage regulator for slow rise of the regulated output.
     
  3. josephhsu

    Thread Starter New Member

    Dec 9, 2008
    2
    0
    Thanks your reply. And I think the second method is better for me due to economic reason.
    I will appreciate you if you tell me how to adjust the regulator rising time?

    Thanks.
    Joseph Hsu
     
  4. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You can use different capacitor values.
     
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