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?

 

Check out this application note; I think it will tell you what you're looking for.

 

Look up the IR HEXSENSE series IRCZxx series for example.
Max.

 

Check out this application note; I think it will tell you what you're looking for.

Excellent, thank you very much.

 

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?

Another possibility.
http://www.allegromicro.com/en/Products/Current-Sensor-ICs.aspx

 

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

 

Another possibility.
http://www.allegromicro.com/en/Products/Current-Sensor-ICs.aspx

Those allegro sensors look very tempting... not that expensive, compact, isolated, and easy to use

 

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

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

 

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