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  • TI Thinks Resolved

PMP15043: cannot start buck converter

Expert 7345 points

Replies: 6

Views: 271

Part Number: PMP15043

Hi, my customer test the board with 12V at Vbus, Vset=5V.

They observed 0 voltage at the output(B+ pin). Then they measured TPS54821 pin8 and pin11.

PIN8(COMP) waveform shown in green below(-0.25V), PIN11(PH) waveform is yellow below. It looks like TPS54821 restart again and again(the time interval is almost 80ms=16384 cycles)

What could we do to fix the problem?

  • Hi Howard,
    the COMP is pulled low by external amplifier. please help to check the current loop and voltage loop input and output. then we can know which loop pull low the COMP pin

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Jasper,
    thanks. The customer will check it after the holiday. I'll give you feedback then.
  • In reply to Howard Zou:

    Hi Howard,
    just closed the post now. reply it after customer has feedback

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Jasper,

    pin6 of U10 is about 8.5V, pin6 of U9 is about 4.5V.

    What else should I check?

    Thanks.

  • In reply to Howard Zou:

    Hi Howard,
    it is unlike to see -0.25V in COMP_BUCK pin if the U10 and U9 output are high. did you measure the correct pin?

    Best Regards

    Jasper Li
    Boost Converter Solution 

  • In reply to Jasper Li:

    Hi Howard,
    I closed the post here and let's keep on through email

    Best Regards

    Jasper Li
    Boost Converter Solution 

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