• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 63 subscribers
  • Views 677 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

UCC2895 SYNC Signal Question

Richard Elmquist
Mastermind 45250 points
Other Parts Discussed in Thread: UCC2895, UCC3895

I have a customer who is using the UCC2895 to drive a half-bridge, ZVS forward converter with phase shift control and have questions regarding the SYNC signal. They have reason to believe that the SYNC signal might be hanging in either a LOW or a HIGH state for undetermined reason and wonder how this affects the internal clock of the device. If the SYNC signal were to “stick” in one of these positions would this cause an issue with the internal oscillator as the SYNC signal is still driving the input even though it is “stuck” in either a HIGH or LOW for extended periods of time.

He is driving the input with an FPGA and believes that it can supply up to 10mA to the SYNC pin. They need to know if this will cause damage to the part or will the internal oscillator take over and drive the outputs. They are having issues with their mosfets and are wondering if this issue could lead to their failure.

Please let me know if you have questions for the customer. I probably can supply some schematic, but it would have to be off-line.

Thanks for your help with this!

Richard Elmquist

  • 0
    TI__Mastermind 31580 points
    Hi Richard,

    I have asked one of the engineers to respond to the post, it may be tomorrow before you see a response.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    TI__Mastermind 25570 points

    Hi Richard

    On the UCC3895

    SYNC getting stuck LO will short the oscillator output at CLOCK to ground. SYNC (Oscillator Synchronization) section of the Data Sheet says that the SYNC pin may be loaded with a resistor as low as 3.9k. I'd expect that shorting the SYNC pin to ground would damage the controller. The internal logic will also stop and the OUTX pins will latch in their current state.

    SYNC getting stuck HI will stop the oscillator and should set CLOCK to 1. This will stop the internal logic with the same results.

    Either of these conditions will likely cause extensive PSU damage.

    I'd advise some form of watchdog on the FPGA output.

    Please let me know if you need any further help on this.

    Colin

  • 0 in reply to Colin Gillmor
    TI__Mastermind 45250 points

    Colin,

    Thanks for your help with this issue!

    I will let you know if the customer has any further questions.

    Thanks again.

    Richard Elmquist