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LMP8480T- current sense amplifier

Smitha R
Intellectual 790 points

Other Parts Discussed in Thread: LMP8480

Hi,

We are using LMP8480T in our power supply unit application. This IC has been used to limit current for  41V DC-DC converter(LM5085MY) if load current exceeds 5A. (VCC for this is 55V-74V, output voltage of DC-DC converter-41V, max load current-5A, sense resistor value-0.012 ohm) But this current limiting circuit is not working as expected.  We tested LMP8480T seperately(IC level) but it is not working.  we are not able to see its output voltage when current is within the limit. 

Our circuit works fine if we isolate this current sense amplifier output. But we would like to know what is happening with current sense amplifier

Kindly request you to advise if we are missing anything.

  • 0
    TI__Genius 15770 points
    Hi Smitha,

    It will be helpful if you share schematic of the system so I can verify all setup. Also, can you describe the test setup you used to test the LMP8480 device separately?

    Regards
  • 0 in reply to Mayrim Verdejo
    Intellectual 790 points

    Hi Mayrim,

    Thank you for the quick response.

    Below is the schematic of current sense circuit.  For testing IC seperately, we soldered IC on general purpose PCB and used function generator to give voltage across two input pins of current sense IC and used DC power supply to give VCC at pin 2. We were not able to see any output at the output pin.

    Awaiting for your advise.

    Thanks,

    Smitha R

  • 0 in reply to Smitha R
    TI__Genius 15770 points

    Hi Smitha,

    I have a few questions:

    1. When testing the LMP device separately:

    a. What is the common mode voltage (Vcm) of your signal generator? Please remember that you need a Vcm of 4V minimum. 

    b. What is the differential voltage that you are applying using the signal generator?

    c. What is your Vcc?

    d. Please take a look at the schematic I have below. I am trying to run some simulations to understand the behavior. Can you please let me know the parameters you used?

    Regards,