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Max current sense chip 
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1N4001 - Signed up
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Didn't know where to post it, so here it is. I know there are folks that like the current sense resistor, this little chip resolves many of the problems of using the current sense resistor.

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5817


Wed Nov 05, 2008 12:30 pm
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QFP80 - Contributor

Joined: Thu Sep 04, 2008 1:54 pm
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Allegro Micro has some current sense ICs too

http://www.allegromicro.com/en/Products ... sensor.asp

They also have great hall sensors for crank/cam applications, stepper motor drivers, etc. All high temp rated.


Mon Dec 08, 2008 3:41 am
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1N4001 - Signed up

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jharvey wrote:
Didn't know where to post it, so here it is. I know there are folks that like the current sense resistor, this little chip resolves many of the problems of using the current sense resistor.

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5817

I don't get it. The part uses a current sense resistor. And I guess too, what are the problems with current sense resistors in this application?

Image


Mon Dec 08, 2008 4:16 am
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1N4001 - Signed up
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MotoFab wrote:
I don't get it. The part uses a current sense resistor. And I guess too, what are the problems with current sense resistors in this application?

The top posted max chip includes the sense resistor. The graphic requires you to add an external resistor, make sure it's calibrated, make sure you don't have antenna /a RF issues, make sure you don't land on some obscure hole or pole (sometimes found in the op-amp transistors arrangements), ect. It includes all of it so you simply run your current path through the chip and bang you have an answer.

About Allegro Micro, they have some great stuff, mostly hall based. I've got a chip that senses up to 100 amps with out breaking the trace to get current to run through the sensor. That's where I got the idea for the setup I've included in FreeEMS 1.0.


Mon Dec 08, 2008 11:45 am
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1N4001 - Signed up

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jharvey wrote:
The top posted max chip includes the sense resistor. The graphic requires you to add an external resistor, make sure it's calibrated, make sure you don't have antenna /a RF issues, make sure you don't land on some obscure hole or pole (sometimes found in the op-amp transistors arrangements), ect. It includes all of it so you simply run your current path through the chip and bang you have an answer.

The link points to MAX9938. http://www.maxim-ic.com/quick_view2.cfm/qv_pk/5817 That component has no internal Rsense. Maybe the pin labels of RS+ and RS- are throwing you?

After reading over the response I have this to offer. RF really can't impress onto a low impedance signal, at least not RF at human-safe power levels. I prolly don't get what you mean about the relevance of op amp nodes in this context. But measuring current with a low ohm Rsense and a differential amp is a common application using commodity components. I don't see a problem, but again, I may not be understanding you.

As brilliant as many of their parts are, Maxim is a boutique house. They make their living on unique parts. Unique parts without multiple sources, that are 16 weeks out when you need them, or the buy order missed the lifetime buy window by a month. It is very easy to get trapped behind that 8-ball more than once.

- Jim


Mon Dec 08, 2008 12:31 pm
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Hmmm, I wonder if the URL now points to a different chip. That's not the specs I remember for the chip I posted about... Or perhaps I simply forgot what the specs where.


Mon Dec 08, 2008 12:48 pm
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