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TPS23756: The controller mode of TPS23756

chentsu chung
Mastermind 6180 points
Part Number: TPS23756
Other Parts Discussed in Thread: TPS23751, TPS23754, TPS23752

Hi,

1. What is the control mode of TPS23756? CCM or DCM?

2. Are all product of this series(TPS23751/2/3/4/6) the same? 

Thank you.

C.T.

  • 0
    TI__Genius 9230 points

    Hi CT,

    1. The control mode of TPS23756 is CCM.

    2. Due to the single gate drive, TPS23751 & TPS23752 are meant for Flyback only. TPS23752 has additional pin to support Cisco's Green Mode. The TPS23754 & TPS23756 have 2 gate drives allowing for active clamp forward or flyback with a synchronous rectifier. TPS23756 has a lower UVLO, so that it can support 12V adapter OR-ing, while the TPS23754 can only do 24V adapter OR-ing.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer

  • 0 in reply to Thomas Amlee
    TI__Expert 5615 points
    CT, When it comes to this question: 2. Are all product of this series(TPS23751/2/3/4/6) the same?

    I think you are asking if all parts are CCM mode. Is that your question?

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

    Yes, I'm wondering to know if all parts are CCM mode.

    BTW, the page 28 of TPS23751's datasheet describe the VFO mode for light-load. But no any description about light-load operation in TPS23756's datasheet . May I know is the light-load operation the same with TPS23756? Or TPS23756 use another way for light-load operation?

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

    Hi CT,

    Yes, all of these ICs are CCM PWM controllers. VFO mode is an optional mode for TPS23751 & TPS23752, only.

    If VFO mode is not used on the TPS23751 or TPS23752, All of these ICs (included TPS23756) will switch at fixed frequency at light load. They will naturally transition from CCM to DCM when the valley of the primary ripple current reaches zero. The output current level when this transition occurs is determined by the size of the primary ripple current, which is designed for by choosing the primary inductance of the flyback transformer.

    Please see section 2.6 of SLVA305C for tips on how to size the primary inductance for a target primary ripple current & SLUP261 for an explanation of these operating modes.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer

  • 0 in reply to Thomas Amlee
    TI__Genius 9230 points
    Hi CT,

    Were we able to sufficiently answer your questions? If so please click the green "resolved" button on the post you found most helpful. If you have additional questions, 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,

    Sorry for the late reply, thank you very much!

    C.T.