Leakage current with a mosfet gate driver

Discussion in 'Power Electronics' started by bkhan10000, Jan 22, 2017.

  1. bkhan10000

    Thread Starter New Member

    Jan 18, 2017
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    Hey guys,

    I am building a circuit that has a gate driver powered by 2 lithium ion cells. My concern is that, if the gate driver is left connected to the batteries, is their a leakage current I should be worried about that may end up damaging my batteries if left too long? I am specifically using a tc4420 and the data sheet doesn't mention anything about a leakage current. Any input is helpful!

    -khan
     
  2. crutschow

    Expert

    Mar 14, 2008
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    It's given as the operating current as shown here:
    upload_2017-1-22_13-56-5.png
    So for minimum current you want the input be at 0V.
    The maximum quiescent battery life would then be the Ah rating of the battery divided by 400μA.
     
  3. bkhan10000

    Thread Starter New Member

    Jan 18, 2017
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    Thank you for the clarification. Is there any way I can limit this to near near zero at zero volts Vin. I am basically trying to make a circuit soldered together that shouldn't be touched. I am wondering how they do this with battery powered devices without letting the battery discharge to a level harming the battery?
     
    Last edited: Jan 22, 2017
  4. crutschow

    Expert

    Mar 14, 2008
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    You need to remove the power to the circuit by some method.
    What is the rest of the circuit doing when this IC is not being used?
     
  5. bkhan10000

    Thread Starter New Member

    Jan 18, 2017
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    It doesn't seem like I can do that. Though I am open to methods to possibly do that as I am still learning. I will post my circuit soon. Rather, are there any gate drivers out there that have much lower leakage current? Say 20 microamps? The driver is driving a very low power mosfet that switches no more than 3 amps at 5 volts.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    What is the MOSFET and how fast do you need it to switch?
     
  7. bkhan10000

    Thread Starter New Member

    Jan 18, 2017
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    Very slowly. In fact switching is maybe once a minute. The mosfet is irf3205.
     
  8. crutschow

    Expert

    Mar 14, 2008
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    So, for that slow speed, you don't need a driver.

    But that MOSFET needs 10V to fully turn on, and assuming each cell is 3.7V, you only have 7.4V total.
    You should really have a logic-level type MOSFET whose Rds(on) in the data sheet is specified at a Vgs of 5V or less.
    The irf3205. is specified at a Vgs of 10V.
    upload_2017-1-23_11-48-41.png

    But for low currents you may be okay.
    How much current do you need to switch?
    What signal level is controlling the MOSFET?
     
    Last edited: Jan 23, 2017
  9. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    And what else is in the circuit that is "leaking" or otherwise consuming current?
     
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