MAX4173 Current sense amplifier

I just built a current sensing application based on a MAX4173. I am suitably impressed with this device. It is extremely versatile and cheap. The MAX4173 allows you to measure the current across a sense resistor with a 28V common-mode range and provides a ground-referenced output proportional to the current across the resistor. I will probably be using one on most of my projects from now on since I do a lot of prototype work and having a cheap and easy way to sense current draw is pretty useful.

IMAG0028

The MAX4173 is available in either an SOT23 or SO8 package, and only requires a decoupling capacitor and a sense resistor to operate. There are three different preset gains available so by combining that with the sense resistor value you can achieve a variety of current ranges.
I used the device in a 4-20mA control loop, with a 20X gain and a 10Ω resistor for a 0.8-4V output into an ATtiny 13’s ADC with a 5V reference. The 10Ω sense resistor is small enough that the loop won’t be affected and large enough to provide good signal range and sensitivity.
For future projects I will probably be using the higher gain version with a smaller sense resistor on the input power line and just leave the MAX4173 output on a header for diagnostic measurement if I don’t have a spare ADC pin. This will limit circuit loading but provide an output for measuring actual circuit current draw.
There is another similar version of the MAX4173, the MAX4080. It can handle higher common-mode voltages and bidirectional current. It’s also a bit more accurate than the 4173, but I haven’t tried it out yet.

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Monday, January 18th, 2010 Electronics

5 Comments to MAX4173 Current sense amplifier

  • Buddie says:
    September 22, 2010 at 5:00 AM

    Thanks josh for the wonderful work and i did sent you a mail with starting id richmondbode thanks

  • abdulaziz says:
    November 17, 2011 at 6:38 PM

    Hi, Mr.Josh, i want to say thak you for the helpfull device and i want to ask where have you bought the MAX4173? because i want to bay one in the U.S, but i could not find a saler exapt for Jameco company. So, please if you know someone else how dose let me know.

    Best regards.
    Abdulaziz

    Aziz-4-4-4-@hotmail.com

  • imsolidstate says:
    November 27, 2011 at 8:31 AM

    Abdulaziz, I got the MAX4173 directly from Maxim. You can order samples from their website.

    http://www.maxim-ic.com/samples/

  • Daddi says:
    February 9, 2012 at 6:24 PM

    Hey Mr. Josh. I am using the MAX4173 for my solar panel project. We are trying to measure and display the voltage and current the solar panel generates. We can successfully measured the voltage but can not measure the current. We are trying to use the MAX4173 to measure the current but I am not sure how it works. Can you please explain ? Does the chip output the exact current through Rsense or the current specified by the datasheet ? Thank you

  • imsolidstate says:
    February 24, 2012 at 2:27 PM

    Hi Daddi, it’s been quite a while since I worked with that chip, but it’s basically an amplifier. You put the sense resistor in series with the colar panel, and the resistance of the resistor causes a voltage drop that is proportional to current. You use a small resisitor so as to limit the effect on the circuit. Then the chip measures the voltage drop, and buffers and amplifies it for use. You decide what the output is based on how you set up the chip. The datasheet can tell you more about how to do it. Good luck!

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