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I am in need of sensing the current in a circuit and cutting off power when current exceeds a threshold which should be about 2A. It seems that everything I've read recommends using separate "current sense amplifier" and "voltage comparator" packages but I would think that this need is so common that someone would manufacture a device that does both in the same package. Board space is limited and I don't need to access the intermediate analog signal between the two devices. I have already tried using just a voltage comparator but it doesn't seem to be sensitive enough by itself to detect the small voltage difference across the current sense resistor.

The device needs to operate with a 12VDC supply. I am setting absolute max voltage to about 13.5VDC so the device should be rated for more than 15VDC.

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closed as off-topic by Ignacio Vazquez-Abrams, Daniel Grillo, Ricardo, PeterJ, Nick Alexeev Aug 7 '15 at 6:31

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  • \$\begingroup\$ Search for electronic fuse or electronic circuit breaker. eg. LTC4213, NIS5112. \$\endgroup\$ – Spehro Pefhany Aug 5 '15 at 16:09
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    \$\begingroup\$ Will a polyfuse not do the job? \$\endgroup\$ – Nick Johnson Aug 5 '15 at 16:27
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If you must use a current sense amp with comparator rather than an eFuse or something like that, TI makes quite a few devices that could work for your application. Here are a couple of examples but you can search the website for more:

http://www.ti.com/lit/ds/symlink/ina202-q1.pdf

http://www.ti.com/lit/ds/symlink/ina300.pdf

http://www.ti.com

Looks like Maxim also has some products that would work:

http://www.maximintegrated.com/en/products/analog/amplifiers/MAX4373.html

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  • \$\begingroup\$ The information you provided is quite useful. Thank you for your answer. I read in an article that low-side current sensing can't detect load shorts. Looking at the diagram I can't see why this is. This is exactly what I want to do. The statement in the article is just above the 2nd circuit diagram. eetimes.com/document.asp?doc_id=1279404 \$\endgroup\$ – Paul McKneely Aug 5 '15 at 17:25
  • \$\begingroup\$ If the load short is to the top of the sense resistor it can be detected. However, the actual system ground (the bottom of the resistor in the schematic) is typically running all over the system (maybe even on a chassis) and a short from the load to that ground provides a path around the sense resistor and therefore can't be detected. \$\endgroup\$ – John D Aug 5 '15 at 17:35
  • \$\begingroup\$ Okay. I am running only the load terminals to outside the box. All I need is to sense shorting these two wires. The system ground will never reach the devices. However, there is the matter of shorting either of the two wires to some Earth Ground that may come back to the system's power ground. If that happens, I think there are more issues, not the least of which is differing ground potentials. I don't think I need to go there. These loads will be mounted on insulated supports to makes sure that doesn't happen. \$\endgroup\$ – Paul McKneely Aug 5 '15 at 17:47

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