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TPS50601A-SP: How the SYNC behaves during start up?

Neli08
Prodigy 190 points
Part Number: TPS50601A-SP

1)  Do you know if there are any commercial PWM utilizing the internal SYNC circuitry for this part? 

* We are having trouble defining how the SYNC behaves during start up?  The block diagram  is not descriptive at all.  Do you know if the chip is designed using the old Unitrode methodology?

2) What is the best practice for applying an external sync signal?

3) I know there is a spice model for this part, is that a good representation?

  • 0
    TI__Genius 14540 points

    The device will use its own internal oscillator if none is applied and will continually look for an external signal.  Once an external signal is detected, after 20us, the device will switch over to using the external clock.  I will need to check with our design team if the device listens for external signal and uses during the start-up process as I don't know.

    I am very doubtful that the model captures the nuances of the SYNC circuitry during startup.

    Safe operation of the the external signal is to power up converter, wait for power good to be asserted, and then apply external signal.  Use RT external resistor to set the initial frequency of the internal oscillator so there is minimal shift in switching frequency once the external sync is used.

    Thanks

    Christian

  • 0 in reply to Christian Yots
    Prodigy 190 points

    Hi Chirstian,

    Per your comment, "need to check with our design team if the device listens for external signal and uses during the start-up process as I don't know."  I'm still waiting to hear back on this, I appreciate your other inputs.

    Thanks

    Neli

  • 0 in reply to Neli08
    TI__Genius 14540 points

    Hi Neli,

    Yes, designer has confirmed that if an external clock is detected, even during the soft start ramp up time, the device will switch from using the internal oscillator to use external clock ~20us after detection.

    Thanks

    Christian

  • 0 in reply to Christian Yots
    Prodigy 190 points

    thanks Christian.