MOSFET driver

Discussion in 'General Electronics Chat' started by mik3, Feb 15, 2009.

  1. mik3

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  2. mik3

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    Anyone? :rolleyes:
     
  3. Audioguru

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    Dec 20, 2007
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    I think a very high frequency at full capacitance loading causes the IC to get hot.
    At a lower frequency then the IC will be cooler.
    Since your load capacitance is 3.3 times higher than what is spec'd then the rise and fall times will be 3.3 times longer plus some additional slowing caused by the heating.
     
  4. mik3

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    The switching frequency will be about 30KHz, I think it will be ok. Maybe I will include a few resistors in series with the MOS gates to be sure.
     
  5. jpanhalt

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    I thought in driving a mosfet gate that it was the gate charge, not input capacitance, that one considered most in design/selection of the gate driver. In your case, the charge is 60nC.

    There are larger drivers made; however, I have a 12V DC drive that has been operating well for 10 years using an LT1158 (500mA) driver for 4 parallel mosfets with similar gate charge. Switching frequency is about 20 KHz.

    John
     
  6. mik3

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    Gate charge is related to the input capacitance.

    It says in the datasheet that it can drive up to 2.5 Amps. It doesn't say if it has overload protection and thus why I am asking.
     
  7. jpanhalt

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    I did use a small gate resistor for each mosfet in the example given.
    John
     
  8. mik3

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    I am planning to do the same just to be sure it won't burn.
     
  9. Ron H

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    The part you selected should be fine at 20kHz. Just in case it's not, HIP4080A is characterized for loads as great as 10,000pF (see Fig. 29).
     
  10. jpanhalt

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    BTW, I just looked up the mosfets I used. In one case, it was 5 IRF1010E and 5 IRF 3205 (top and bottom), with the single, LT1158 driver. Based on that, your controller should not have a problem. The IRF1010 has 130 nC gate capacitance.

    John
     
  11. mik3

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    I hope it will be fine ;)
     
  12. mik3

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    What values do you suggest for the bootstrap capacitors?
     
  13. jpanhalt

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    I used 0.1 uF as shown in the datasheet for the LT1158 at the time. I did very few calculations in those days.

    I suspect you have the IR application note of mosfet gate drives (MGDs) number AN-978. On page 6 there is a formula to use to calculate the bootstrap capacitor. I have not tested that formula against the design I am using.

    John
     
  14. mik3

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    I don't have it but I will have a look at their website.
     
  15. jpanhalt

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  16. mik3

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    What do you mean?
     
  17. jpanhalt

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    I mean I have lots of application notes and other things I have picked up on the Internet for personal use. When I try to reference them, I often don't have the original link and don't like posting the entire, sometimes lengthy document.

    For the past 8 month or so, I have tried to be more conscientious and keep an index of links along with the pdf files. What I meant by my comment was that it would be nice if the Internet link could be easily and automatically saved with the pdf, so I wouldn't have to keep the separate index and would be able to give the proper credit when needed. I don't like just saving the link, because my connection is sometimes down, often slow, and some AN's simply disappear.

    John
     
  18. Ron H

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    John, that's a great idea! I wonder if Google could somehow do that?
     
  19. mik3

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    In my opinion, there is no need to save each application note link. If you save the link of the main website then you can access all the application notes included in the website.
     
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