Using MAX4372 to sense current on negative supply.

[kvn17]

max4372

Hello,

Anyone here familiar with using the MAX4372 current-sense amplifier to sense current on a negative supply?

The App notes on a similar device MAX4172 shows that you can by conneting the Gnd pin to negative supply. Can I do the same with MAX4372?

App Eng thinks you can. But suggest I try it. Unfortunately I do not have part to try. Parts is coming in butI would like to know as soon as possible.

Any help would be appreciated it.

Thanks,
kvn

 

[IanP]

Keep in mind that the MAX4372 is a ‘high-side’ current sense IC, so, if you try to use it on the negative supply you will have to place Rsense on the 0V rail and the output voltage will be referenced with regard to the negative rail ..
If you can accommodate these “small” differences then maybe it’s possible, however, 0V won’t be GND-reference any more ..
I know, this is an off-the-shelf solution, but if you would like to do it properly you should really sense current on the negative rail; this can be done with a typical opamp connected between [+V] and [-V] with 0V[GND] as the reference and Rsense on the negative rail ..

Regards,
IanP

 

[kvn17]

Thank you IanP. The opamp solution that you've suggested worked beautifully.

I'm also using the MAX4372 for sensing other + voltages and I would like to keep the common off the shelf part if possible.

Part is coming in this Monday. Internally, I don't know how the MAX4372 is hooked up. But from the simple block diagram, it should work right?

Anyhow, will let you know if this works or not.

Thanks,
kvn