Circuit for removing voltage spikes

Discussion in 'The Projects Forum' started by robby991, May 21, 2009.

  1. robby991

    Thread Starter Active Member

    Dec 17, 2007
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    0
    Hi everyone. I have a LabVIEW controled power supply which is the power source to a cmos fabricated integrated chip. This power supply is being told to turn on and off, and I was wondering how I can protect my chip from the voltage spikes associated with the power supply each time it is turned on. Is there some sort of circuit I can build to ensure there will be no voltage spikes? Can I just run it through a schmitt trigger?
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use a low pass filter and a fast zener diode to absorb the spikes.
     
  3. robby991

    Thread Starter Active Member

    Dec 17, 2007
    79
    0
    Thanks mik3. So essentially all I am doing is using the zener diode as a voltage regulator circuit? My input voltage is 2.5V, which is what I would like my output voltage to be. So I would use a 1N5223B 2.7V zener diode in the circuit I attached. So any Vin spikes produced would induce a current through R2 which would get absorbed by the zener. How would I go about calculating the value of R2 if I don't know exactly how large the spikes will be, and hence the voltage drop between the zener and spikes? I read that Zeners come in 2.4 and 2.7V, but I will need exactly 2.5 V, will it be possible to get this with this circuit?

    I had another idea so overcome this spike issue and I was wondering what you guys thought. Use a tristate buffer, the enable line is controlled by Vin, and the tri-state input is wired high to Vdd (2.5V). Everytime the enable line goes high, Vdd will be passed to my chip, independent of the spikes.
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,659
    632
    Or, buy a good power supply that doesn't make spikes when turned on or off, and then keep the cables from the power supply to the circuit short (less than 10 meters!).

    Its a good idea to put bypass capacitors on the board just to keep control of the power supply impedance at high frequencies.
     
  5. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Use a 2.7V zener. The value of the resistor depends on the power ratings of the zener but since a spike lasts a few ms you don't need to worry about exceeding the power dissipation of the zener. Also, you have to consider the peak current the zener can conduct in the calculation of the resistor.

    What is the pulse supposed to drive?
     
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