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LM5176: Load current is only 0.3A, LM5176 enter the protect mode.

Amelie Zheng
Genius 10865 points
Part Number: LM5176

Hi Team,

The attached file is designed by customer. They found that when load current is only 0.3A, LM5176 enter the protect mode.

Could you kindly help to check the SCH?

5238.LM5176.pdf

  • 0
    TI__Genius 10865 points

    I talked with customer to get more detail. The input  of LM5176 is from power supply, which setup as 24V. Want to use LM5176 to convert 24V to 12V.

    The test is disconnecting R615/616/617/618 to disconnect super cap C14/16/17/19/23. And then connect LM5176 to electronic load.

    When electronic load of LM5176 is 0.2A, LM5176 is normal. The supply power of LM5176 is 24V/0.15A...

    When electronic load of LM5176 is 0.3A, LM5176 is abnormal. The supply power of LM5176 is pulled down, only  4V/5A...

    Why? LM5176 could be 10A output. Why only 0.3A, it can't work normal.

  • 0 in reply to Amelie Zheng
    TI__Guru 65580 points

    Hello Amelie,

    Would it be possible to check with a different load?

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    TI__Genius 10865 points

    Hi Brigitte,

    Customer only have one electronic load. They test again when electronic load of LM5176 is 0.3A and wait about 8 second, and found that LM5176 could rise to 12V from 4V. But when continue to increase 0.3A to 2A, the electronic has alert that current is over.(but the electronic load could setup max 400V 40A)

    Are there anything wrong in customer's SCH? the indictor of the SCH is 2.2uH. customer also try to short pin 13 and pin 14. But still doesn't work,

  • 0 in reply to Amelie Zheng
    TI__Guru 65580 points

    Hello Amelie,

    Would you please test with R1 shorted and with a reduced SLOPE capacitor.

    The schematic looks OK, only R1 should be placed in the middle of the output capacitors to minimize noise.

    They could as well increase the filter capacitor from CS to CSG.

    Best regards, 

    Brigitte 

  • 0 in reply to Brigitte
    TI__Guru 65580 points

    Hello Amelie,

    As I did not hear back from you, I expect you have been able to solve your issue. I will close this thread now. If my assumption is wrong, please post below or start a new thread if this one is already locked.

    Best regards,
    Brigitte