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LP8860 SEPIC

Kei Sato73562
Expert 2310 points

Hello,

I have some question of LP8860

Q1

Can LP8860 support SEPIC?

Q2

I am connected to the LED 4 series and want to drain 600mA.

Is such a connection possible?

For details, please watch an attached file.

Kei

LP8860 SEPIC.pptx
  • 0
    TI__Guru 69942 points

    Kei,

    The appropriate applications engineer has been notified of your inquiry. They will get back to you with a response shortly.

    Regards,

    Eric

  • 0 in reply to Eric Hackett
    Expert 2310 points

    Hello, Eric

    Do you have update?

    Best Regards,

    Kei

     

  • 0 in reply to Kei Sato73562
    Expert 2310 points

    Hello Eric,

    About Q2

    The application of the 300mA string is in Fig62 of data sheet p91.

    Therefore I think that the 600mA string is done at LP8860.

    How about it?

    Best Regards,

    Kei

  • 0 in reply to Kei Sato73562
    TI__Guru 69942 points

    Kei,

    I apologize for the delay in response, I didn't realize there hadn't been a response to this request. Unfortunately, I do not support these parts, so I cannot adequately answer your question. This post has been escalated to high priority and will receive an answer promptly.

    Again, I apologize for the delay.

    Regards,

    Eric Hackett

  • 0 in reply to Eric Hackett
    Expert 2310 points

    Hello Eric

    When can I have an answer about a question of LP8860?

    Best Regards,

    Kei

  • 0
    TI__Prodigy 460 points

    Hi Kei,

    Kei Sato73562 said:

    Q1

    Can LP8860 support SEPIC?

    yes, LP8860 can support SEPIC with extra diode and resistor which help to prevent OCP fault

    Please be aware - minimum  voltage is 16V, looks like you would like to have 14V.

    Kei Sato73562 said:

    Q2

    I am connected to the LED 4 series and want to drain 600mA.

    Is such a connection possible?


    Yes, all outputs can be tied together to increase current; BTW you can use phase shift in this case, maybe it is not explained very clear in DS.

    Best regards,

    Vladimir

  • 0 in reply to V.Trondin
    Expert 2310 points

    Hello Vladimir,

    Thnak you for your replay.

    I have additional question.

    Is it necessary to add additional components? (Diode + 1kohm)

    What kind of meaning do you have of additional components?

    If it is SEPIC circuit, the electric current does not flow even if the output short-circuits.

    Best Regards,

    Kei

     

     

  • 0 in reply to Kei Sato73562
    TI__Prodigy 460 points

    Hi Kei,

    actually LP8860 was not designed for use in SEPIC mode, but can be used.

    Problem here during starup - if LP8860 doesn't not see any voltage at FB pin during startup - logic decides it is a boost output short condition and starts recovery algorithm. To prevent  this situation during startup should some voltage appears at FB pin, this is reason why I put resistor and diode on schematic. Values, as you understand, are not critical - any diode and 1...100k resistor.

    Best regards,

    Vladimir