High Side Switch Suggestions

Discussion in 'The Projects Forum' started by jwilk13, Jul 8, 2011.

  1. jwilk13

    Thread Starter Member

    Jun 15, 2011
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    Hi again,

    I have what seems to be a fairly simple question regarding the selection of a high side switch. Here is some helpful info:

    My signal is a 0-3.3V PWM signal from a microcontroller, and I'm looking to control a proportional valve with a max load current less than 3 amps (inductive load). Normally, I would use an N-channel MOSFET with a flyback diode and snubber circuit, but I'm limited to high side switching with this application. My initial thought was to use a P-Channel MOSFET, but I came across some nifty devices that seem like they might work for my application. One example would be the ITS428 from Infineon. If I used this device, it seems like I wouldn't need to use a MOSFET driver or a snubber circuit, which would be nice.

    Does anyone have experience with these devices? If so, would it work for my application? I'm going to contact Infineon as well and see what they have to say. Thanks in advance.

    John
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. jwilk13

    Thread Starter Member

    Jun 15, 2011
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    I noticed that too, and it might be a problem. I'm going to order some anyways and give them a shot. My uC outputs slightly less than 3.3 V (it's closer to 3). Could I clamp my uC output to say 3v with a zener diode to stay below that 3.2v just to be safe? Any thoughts?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    The problem is that you might have to get the input above 3.2v in order for it to consider that to be a logic "1". If your uC output is only 3v with no load, then there is a chance that it will not work due to the stated specifications.

    If you tried clamping the uC output to 3v, you would simply make the problem much worse.
     
  5. jwilk13

    Thread Starter Member

    Jun 15, 2011
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    12
    Oh I was thinking of it as I couldn't exceed the max rating of 3.2v. I figured as long as it's between the minimum (1.7v) and maximum (3.2v) it would be okay. But now I see that it's saying it could regard UP TO 3.2v as logic 1.

    Hopefully that maximum isn't the case with the ones I order :p. I'll get them in next week and let you know what happens and what I destroy. Thanks for the help.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    You still don't quite have the idea.

    The threshold for it to recognize the input as a logic 1 can be anywhere from 1.7v to a maximum of 3.2v. That means you will have to exceed 3.2v in order to be guaranteed that you have told the device to turn it on. Your mileage can (and will) vary.
     
  7. jwilk13

    Thread Starter Member

    Jun 15, 2011
    228
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    Reading back over my previous post, my grammar was a bit off. We're on the same page :)
     
  8. jwilk13

    Thread Starter Member

    Jun 15, 2011
    228
    12
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