• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 1658 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Original question:

UCC3895: Maximum duty cycle of UCC3895

TINA/Spice/UCC2895: How to connect sync pin when two UCC3895 is used for DC-DC Converter

roh hagrae
Prodigy 20 points
Part Number: UCC2895
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hi?

I am james and these days I have a seious question on ucc2895

I want to connect two UCC2895 circuits in parallel.

but I don't know how to handle sync pin

please answer my question

best regards

  • 0
    TI__Mastermind 25570 points

    Hello James

    The SYNC pin on the UCC2895 is bi-directional. When operating as an OUTPUT the internal clock frequency will appear at this pin. When operating as an INPUT the internal clock will synchronise to the frequency at the SYNC pin. This synchronisation function can increase the oscillator frequency only.

    You should connect the two SYNC pins directly together. The two controllers will SYNC up to the higher of the free running frequencies of the two devices. the free running frequency of the two controllers can be set to the same value - component to component differences will mean that one of the devices will run faster than the other. The slower of the two devices will then synchronise up to the faster.

    Do check that starting and stopping behaviour is ok - ie when VDD is applied and removed.

    Regards

    Colin

  • 0 in reply to Colin Gillmor
    Prodigy 20 points
    Thank you for your correct answer
    I connected two sync pins directly together and two PSFB driver UCC2895 is working well
    but I have another question, that is like this

    If connecting directly sync pins then two PWM A signals are always same phase ?
    according to experimental, sometimes PWM A signals have same phase but sometimes are different
    I wonder if parallel operation is possible even though PWMs are not in phase with each other.
    Please answer one more

    best regards
  • 0 in reply to roh hagrae
    TI__Mastermind 25570 points
    Hello Roh

    Yes, parallel operation is possible and you can connect the Vout outputs of the power stages together. The devices will sometimes synchronise in phase and sometimes out of phase - this is the expected operation of this device.

    I've been out of the office for a while without access to emails so that is the reason for the delay in response. Please let me know if you have any further questions.

    Regards
    Colin