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TPS2373: Schematic review

chentsu chung
Mastermind 6180 points
Part Number: TPS2373
Other Parts Discussed in Thread: UCC2897A, PMP21318

Hi,

Could you please help to review the schematic for TPS2373 and UCC2897A, thank you.

TI_BT.PDF

Please help to remove the attached file while starting review, thank you.

C.T.

  • 0
    TI__Genius 9230 points
    Hi CT,

    I'll give comment this morning.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer
  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points

    Hi CT,

    - Reduce Vdd-Vss capacitance to <0.12uF for compliant detection
    - APD voltage divider is set too low. Keep it away from APD abs max of 6.5V. Under 5V is recommended.
    - Be sure that input bulk capacitance is at least 100uF (CE10)
    - CE4, C77, C78, C76, C15 should be reduced to 2.2uF
    - consider using the feedback values from PMP21318 (see attached schematic & BOM
    - gate drive circuit for U40 should be a linear regulator (rather than direct driven) to keep Vgs under max
    - Output capacitance is excessive, consider lowering to single 220uF & adjusting as necessary (see PMP21318)

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer

    6318.PMP21318_RevA(001)_Sch.PDF

    4812.PMP21318_RevA_TI-BOM.xls

  • 0 in reply to Thomas Amlee
    Mastermind 6180 points
    Hi Tom,

    Thanks for your great help, but may I ask about the 2 answers below? The big cap used at input and output, should lower the ripple noise of system, am I reght?

    - CE4, C77, C78, C76, C15 should be reduced to 2.2uF
    - Output capacitance is excessive, consider lowering to single 220uF & adjusting as necessary (see PMP21318)


    C.T.
  • 0 in reply to chentsu chung
    TI__Genius 9230 points
    Hi CT,

    You are correct, the big bulk capacitors on the input & output will lower output ripple. For sizing these components to meet a certain peak to peak ripple spec, see section 2.7.4 & 2.7.6 in the our flyback design guide: www.ti.com/.../slva305c.pdf

    On the input filter, the larger bulk capacitors before the inductor do the majority of the ripple filtering, while the smaller capacitors after the inductor provide bypass for switching energy. To clarify my recommendation, CE4 should be removed or moved before the inductor and C77,C78, C76, & C25 should each be increased to 2.2uF (much like PMP21318)

    if output capacitance is too large, the dominant pole may attenuate too much & reduce bandwidth . See section 2.9 of the design guide for details.

    Regards,
    Tom Amlee
    PoE PD Apps Engineers
  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points
    Hi CT,

    Were you able to find the support you need? If so please click the green "resolved" button on the post you found most helpful. If you are still working on your issue, then feel free to respond & we can continue providing support.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer
  • 0 in reply to Thomas Amlee
    Mastermind 6180 points
    Hi Tom,

    Yes, of course, thanks for your always support!!!

    C.T.