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Circuit drawing mostly constant current

  1. Dec 21, 2012 #1
    Hello. I have an integrated circuit that draws current in pulses. The pulses have a duration of about 0.5 ms and a period of 2 ms. I need to make a circuit to put in front of this IC that will smoothen out these current pulses. One option is just to use a resistor and a capacitor. When the IC needs current it will draw it from the capacitor and the capacitor is then recharged through the resistor. But I was wondering if there are better solutions out there?
     
  2. jcsd
  3. Dec 21, 2012 #2
    No, a capacitor is best, that is why some chips have capacitors across their power rails and physically adjacent on the board. Something about 100μ is usual.
     
  4. Dec 21, 2012 #3

    NascentOxygen

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    There are a number of ways to go about it. Please explain why you need to.
     
  5. Dec 21, 2012 #4
    I need it because the sharp current peaks (dI/dt) are creating magnetic fields which are inducing noise in a magnetic field sensor I have.
     
  6. Dec 25, 2012 #5

    NascentOxygen

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    Then follow Studiot's advice on installing extra filter capacitance close to the IC and use short leads. If space allows, use a selection of capacitors in parallel, e.g., 47uF, 0.47uF, and 0.022uF to minimize parasitics.
    http://img803.imageshack.us/img803/4666/holly1756.gif [Broken]
     
    Last edited by a moderator: May 6, 2017
  7. Dec 25, 2012 #6

    sophiecentaur

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    Agreed; keep any leads which are downstream of your filter really as short as you can and possibly even twist them together to reduce external magnetic fields. The filter could be made better if there's a series inductor included, too.

    One question worth asking is whether the interference you are getting is really external magnetic or is it getting down the supply to your sensor? Perhaps a separate regulator for the sensor could help.
     
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