Current-Sensing Mosfet

Discussion in 'General Electronics Chat' started by cmartinez, May 31, 2016.

  1. cmartinez

    Thread Starter AAC Fanatic!

    Jan 17, 2007
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    I've been working on a project that may or may not require current monitoring at a Fet's output, and so far the only technique that I've been learning is the one that uses a sense resistor and an op-amp to get an output voltage that is proportional the the current through the resistor.

    But after doing some browsing around, I found this very strange component, which is a Current-Sensing N-Fet. I did some googling, and this is what I found about this technology.

    Does anyone here know how they work and how to use them? Or perhaps point me to a proper application note that I could study?
     
  2. OBW0549

    Well-Known Member

    Mar 2, 2015
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    Check out this application note; I think it will tell you what you're looking for.
     
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  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Look up the IR HEXSENSE series IRCZxx series for example.
    Max.
     
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  4. cmartinez

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    Excellent, thank you very much.
     
  5. ronv

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    Nov 12, 2008
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    Another possibility.
    http://www.allegromicro.com/en/Products/Current-Sensor-ICs.aspx
     
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  6. jpanhalt

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    Jan 18, 2008
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    You can also just sense Vds(on) across an ordinary mosfet. I saw a circuit for doing that several years ago. If that approach interests you, I will try to look it up. Don't know how it compares in accuracy to the other methods. A brief search didn't find it, but here are some similar approaches:

    http://www.cel.com/pdf/appnotes/an3024.pdf

    Device with Vds built in:
    http://www.infineon.com/dgdl/Infine...N.pdf?fileId=5546d462533600a4015355a82da21342

    Controller with circuit built in:
    http://www.ti.com/lit/ds/snos738h/snos738h.pdf

    John
     
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  7. cmartinez

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  8. cmartinez

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    Wow, John. Those are extremely interesting documents... thanks!
     
  9. cmartinez

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    The LM9061/-Q1 High-Side Protection Controller seems promising, since it has inherent over current protection.
     
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