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TLV333: High Side Current Shunt Op-Amp Circuit to Single-Ended ADC for Cost-Optimized Monitor

Part Number: TLV333

Tool/software:

Hello All,

I have a system like 48V input and max 25A, if I use this circuit for this values is it okay?

https://www.ti.com/lit/an/sbaa353a/sbaa353a.pdf?ts=1729192792070

Regards

  • Hello Oben,

    The load is high side and the current sense is low side. +15V or +48V doesn't matter, unless the 1mili ohm resistor opens up. Then a larger Rg 

    25A is a 'large' 25mV input so the gain need to be lowered. If full ADC range is 27A; then gain should be 5V/0.027= 185.2,  so increase both Rg to 690k/185.2 = 3.73k ; closest 1% is 3.74k

    If 1mili ohm did open up, (48V - 5.6V) / 3.74k = 11.3mA; just over the ABS MAX input current. So if this is possible, go further.

    (48V-5.6V) / 10mA = 4.24k ; so pick Rg bigger than that. Then pick Rf resistors based on what max current range to measure. 

  • Hello Ron!

    Thank you for your good feedback.

    I made my voltage supply 3.3V for TLV333 and I made 1.5k Ohms resistors to 6.8k Ohms and when I calculated the max A is 32.52A.

    What do you think about this is this works right?

    Regards

  • Oben,

    Checking fault current, (48V -3.3V - 0.6V) / 6.8k = 6.4mA input pin current (this flows to 3.3V bus that has to absorb this current); that is under 10mA. 3.3V / (690k/6.8k) = 32.52mV = 32.52A

    690k is an odd value, 680k is far more popular. 3.3V / (680k/6.8k) = 32.52mV = 33A

  • Ron,

    So 680k and 6.8k is okay for my wants right?

    Regards

  • Oben,

    Yes this satisfies the DC performance.