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TPS92641: Output current question when use UDIM

Bryan Huang
Intellectual 445 points
Part Number: TPS92641

Hi Team

My customer use UDIM, output current has only peak 10A, not platform.

He wonder know why has only peak. is it been current limit.

Input=16V

Viadj=2.5V,

Rcs is 0.125 ohm

LED is 10A. 2 parallel, total output is 4.2V/20A,

  • 0
    TI__Mastermind 28655 points
    Hello Bryan,

    Viadj = 2.5V means Vcs = 0.25V. If Rcs is 0.125 ohm current is 0.25V/0.125 ohm = 2A. I assume there is a large output capacitor on this design. That is probably what is causing the current peaking, recharge of the output capacitor. Rcs needs to be 0.0125 ohm for 20A when Iadj is 2.5V. Vcs is Viadj/10.

    Regards,
  • 0 in reply to Irwin Nederbragt
    Intellectual 445 points
    Hi Irwin
    Yes,it's 0.0125 ohm, it's my mistake.
    Increase output capacitor value whether improve this situation?
  • 0 in reply to Bryan Huang
    TI__Mastermind 28655 points

    Hello Bryan,

    No, something else must be wrong.  If the regulation point is set to 20A and you see 2A then either the measurement is incorrect or something is not working correct.

    What is the power source to this?  Can you monitor the input voltage and see if it is stable or if the source is dropping?

    Can you run this without the PWM and see where it regulates steady state?

    Can you check the oscilloscope and make sure it is reading correct?

    Regards,