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LM25141-Q1: Vccx connected to 5V Vout affecting current limit

Jingyuan Zhao1
Prodigy 440 points
Part Number: LM25141-Q1

Hi team,

My customer is using LM25141-Q1 for 12V input 5V output with a maximum load of 15A. Schematic is similar to this with L=3.3uH Rsense=0.004ohm Fsw=440K.

When VCCX is connected to GND, it's capable of providing about 15A load; but when VCCX is connected to Vout, it will enter hiccup mode at ~12A load. Any suggestion on what's wrong or where should I troubleshoot from?

Thanks so much.

Best regards,

Charles Zhao

  • 0
    TI__Mastermind 40040 points

    Hello Jingyuan,

    How is the CS and Vout routed back to the IC?  Does this routing change in any way when you take Vout to VCCX when comparing the two configuration?  Is so, suggest taking a separate line from Vout to VCCX and do not use the Vout [CS] line for VCCX?  Do you have an RC filter on Vout and CS inputs to the device?  If not, suggest implementing RC filter as per EVM schematic.  Is the Vout and CS traces routed back to the device deferentially?  If not may need to modify layout.

    Hope this helps?

  • 0 in reply to David Baba
    TI__Prodigy 440 points

    Hi David,

    Thanks for your reply. I think Vout and CS traces are routed back to the device deferentially and I'm not sure for VCCX line.So I'll check with my customer and review their layout first. And I do remember they have RC filter in the schematic but with R=0 ohm and C not placed during test. I'll also try using the RC value recommended in EVM.

    I'll keep you posted and really appreciate your help.

    Best regards,

    Charles Zhao

  • 0 in reply to Jingyuan Zhao1
    TI__Mastermind 40040 points

    Thanks Charles,

    I will close the thread for now.  If you still have issues, please feel free to reopen.  Thanks.