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TPS25846-Q1: voltage measurement on IMON pin

Jacob Wyrick
Expert 6225 points
Part Number: TPS25846-Q1

Hi team,

I'm looking for ways to monitor the current that's flowing through the buck output of the TPS25846-Q1 to check for potential current issues.

Am I able to directly measure the voltage on the IMON pin of TPS25846-Q1 and feed it to an MCU?

What if I add a buffer op-amp to provide high-impedance measurement?

Thanks,

Jacob

  • +1
    TI__Expert 4710 points

    Hi Jacob,

    Adding a buffer is going to give the best result since you aren't adding additional load to IMON.

    If you connect directly to an MCU, you should consider the pin's input impedance/leakage in parallel to RIMON.  Using the datasheet examples of RSNS = 15mOhm, RSET = 300 ohm, and RIMON = 4.02 kOhm - if I have a 3 A load, I can assume I_IMON = ISET/2 = 75 uA.  Without a probe (that is, just RIMON) connected, VIMON = 301.5 mV.  With the 1M parallel resistance of the probe, VIMON = 300 mV.  This voltage ultimately controls the amount of cable compensation.

    Regards,
    Eric

  • 0 in reply to Eric Hartigan
    TI__Expert 6225 points

    Thanks Eric! 

    It sounds like it's totally possible, but we'll need to be careful because any external impedance can ultimately impact the cable compensation performance. However, if we know and accept that, we should be okay.

    I appreciate the quick response!