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UCC28070: UCC28070 multiphase connection

Derek Chan1
Prodigy 190 points
Part Number: UCC28070

Hi,

I would like to interleaved 2 x UCC28070 controllers to form a four phase PFC. Except SGND, IMO and  RDM. Which pins of the controller should I connected together? 

Derek

  • 0
    TI__Mastermind 34465 points

    4phase..pdfHello Derek,

    The concept for a four phase system with the UCC28070 is shown in figure 18 of the data sheet.

    A copy of this diagram is attached.

    Regards

    John

  • 0 in reply to John Griffin1
    Prodigy 190 points
    John,

    Is it a must VAO, SS, VINAC, Vsense short together between the two controllers? As we are using two controllers on two different modules, the mentioned pin cannot simply short together. Is there any problem if these pins are not connected together?

    Derek
  • 0 in reply to Derek Chan1
    TI__Mastermind 34465 points
    Hi Derek,
    I understand your issue better now.
    Having separate connections for the SS pin is probably not going to cause a problem but because of component value variations between the two modules this may result in some discontinuity in the soft start time.
    With a common connection for VINAC and VAO the current demand signal ( this is the output of the multiplier) is the same for both UCC28070 controllers. This means that the current is shared equally.
    If VINAC and VAO are separate connections there is a danger that one module supplies more current than another because of small variations in component values or noise pickup issues in the pcb traces.
    This might result in an abnormal response during a load transient or a line step.

    Also the Figure 18 in the data sheet is a concept drawing and there is no reference design available for a four stage interleaved design.
    It may be possible to design the circuit you propose and all I can do is point out some potential issues.
    Hopes this helps.
    Regards
    John
  • 0 in reply to John Griffin1
    TI__Mastermind 34465 points
    Hi Derek,
    I am going to mark this post as resolved since there has been no response for over a week.
    If you have further queries please open a new post.
    Regards
    John