Mosfet driver

Discussion in 'The Projects Forum' started by vandaycalta, Apr 7, 2016.

  1. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    Can anyone tell me if I can use a mosfet driver to drive a n channel mosfet with a microcontroller. I can not find one(mosfet) suitable for my needs that is also having a logic level gate. Can I use a mosfet driver to control the mosfet with a microcontroller such as an arduino?


    Val
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Yes, a Microcontroller can send signal to the driver, the driver applies gate voltage to MOSFET.

    Post driver and MOSFET that you plan to use.
     
  3. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    Thank you for your reply.
    I am looking at a mosfet similar to this:FCB36N60NTM.
    As for the driver for the mosfet, that is what I dont know on how I would choose one. I know that the microcontroller output will be 5v and 20mA max.

    Val
     
  4. crutschow

    Expert

    Mar 14, 2008
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    How fast do you need to switch it?
    What are your needs that they can't be met with a logic-level MOSFET?
     
  5. tracecom

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    Apr 16, 2010
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    You will be able to drive that MOSFET directly from the uC. Connect an output from the uC to the gate of the MOSFET through an (optional) 330 ohm resistor. Use a pull down resistor (100k) from the gate to ground. Connect the source to ground and the drain to the load. A high output from the uC will turn the MOSFET on and switch ground to the load.
     
  6. dannyf

    Well-Known Member

    Sep 13, 2015
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    Yes, you can the driver doesn't know if it is driven by an arduino or a xrduino.

    Voltage and peak current are two key specs, in addition to topology (high side, low side or half bridge, etc.) Puck your MOSFETs based on your load. Figure out its gate charge, and switching frequency. Then you have peak current. Give your self some room over that.
     
  7. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    I was unable to find a n channel mosfet that I could use w/ a logic level gate that was 600v and 36a. I want to switch this load up to 600 hz.
     
  8. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    Thanks for your reply.

    Do I have to think about saturation with a mosfet and wanting to use it as a switch? Thats where I get confused as I dont want it in the active region.
    Thanks for your help.

    Val
     
  9. tracecom

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    Apr 16, 2010
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    The MOSFET you linked to is logic level; it switches on at 4V or less. And if you read my previous post, it tells you how to switch the MOSFET on.
     
  10. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    I now see the Vgs threshold is 2v min and 4v max so a logic level of 5v will work with this mosfet. I also thank you for your additional information regarding the pull down resistor and the 330 gate resistor. Im trying to learn and also trying not to offend anyone at the same time.

    Val
     
  11. GopherT

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    Don't worry about offending anyone. Someone will always figure out a way to be offended but we all keep coming back. Just ask away.
     
  12. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    Thank you for your kind words. How can I tell on the data sheet if the mosfet I want to use will switch fast enough? Can you tell me what I would be looking for? I am looking to switch around 600hz.

    Val
     
  13. GopherT

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    Nov 23, 2012
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    This is a high speed MOSFET and 600 Hz is easily achieved. The input capacitance (or input charge) is the key variable that determines speed of the mosfet. This one can handle 1000x what you need.

    Are the pins on your Arduino output 5V? Or 3.3V? Or, when in the high state, something in between?

    The MOSFET you selected does have threshold voltage of under 5 V but the graph is for a TYPICAL part out of a day's worth of manufacturing. Note that the datasheet only specifies on resistance at 10V gate-source voltage. I hope you get a part that saturates at 5V. The manufacturer dies not list this part as "logic level" Vgs. The Digikey site categorizes this part as Standard and not as Logic Level (e.g 10V).
     
  14. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    I do see what you mean on the input capacitance. I also see that this part is listed as standard. So you are saying that this part may not act as a switch and have its threshold at 5v due to the fact that it is a mass produced part and the one tested for the data sheet had the specs as recorded? If this is the case would it be wiser or safer to use a mosfet driver with this mosfet?

    Val
     
  15. vandaycalta

    Thread Starter Member

    Mar 22, 2016
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    THe pins on my micro are 5v with a max current of 20ma.

    Val
     
  16. ronv

    AAC Fanatic!

    Nov 12, 2008
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    What you have will probably work, but it is not ideal. At 5 volts the fet is not turned on as good as it would be at 10 or 12 volts.
    With 15 or 20 ma of gate drive current it will switch kind of slow. To get an idea you can divide the Nc value by the gate current so 87Nc / .02 = 4.3 usec. This alsohe ats the fet up a bit since during this time it is kind of half on and half off. Not to bad at 600 Hz but if you decide to run it faster it will start to add up.
    Tell us more about what you are driving with the fet.
     
  17. shortbus

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    Sep 30, 2009
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    Isn't 330 ohm kind of high for a gate resistor? I would think 33ohm would be more like it, according to most Application notes on mosfets.
     
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  18. GopherT

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    Nov 23, 2012
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    I always use 10.
     
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  19. tracecom

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    Apr 16, 2010
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    My thinking is that the resistor is there to protect the uC from the unlikely event of the MOSFET gate being shorted to ground. As I posted, the resistor is optional, and the truth is I often leave it out entirely.
     
  20. tracecom

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    Apr 16, 2010
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    Further to my previous post, I have always wondered why some schematics show a small (<100 Ohms) in the gate lead to a MOSFET. If there is a real need for it, I would be pleased to know what such a resistor is for (no sarcasm intended.) Thanks.
     
    Last edited: Apr 9, 2016
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