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TPS54360 External clock how much would be sweep range?

Bob Lee62837
Mastermind 7230 points
Other Parts Discussed in Thread: TPS54360, TPS54160, LM3495, LM5022

Dear support member,

My Customer use TPS54360.

Customer are thinking the sweep signal of 280kHz ± 10kHz at an external clock.
It think spread spectrum for EMI reduction.


In this case, Is it possible synchronization？

If synchronization is possible,
how much would be sweep range?


Best regard.
Bob Lee.

  • 0
    TI__Guru**** 191445 points
    I have only done some informal experiments with this using a similar device. It was several years ago and I think I used TPS54160. In that case I believe I used linear FM modulation of the clock frequency and visually compared the clock signal to the output switching node. The TPS54x60 would maintain frequency and phase lock up to about +/- 5 kHz. Between +/- 5 kHz and +/- 10 kHz, the frequency was maintained, but the phase relationship was not consistent. Above +/- 10 kHz, the TPS54x60, could not track either frequency or phase. This was for linear frequency sweep only and was a subjective measurement based on visually comparing waveforms. So far as I know there is no official testing for frequency sweep of TPS54360.
  • 0 in reply to JohnTucker
    TI__Mastermind 35185 points

    The TPS54360 will have the same performance as the TPS54160. The important factor is the rate of change of the frequency in the spread spectrum because the circuit which locks the switching frequency to the input clock has a limited bandwidth. I did some evaluation of this measuring the delay from the input clock falling edge to the SW rising edge. With no modulation the jitter in the delay was about 5 ns, with 0.1 kHz/us modulation about 7 ns and with 1kHz/us modulation about 30 ns.

    When the input clock frequency change is too fast the switching frequency doesn't frequency lock and will "chase" the input clock frequency.

    Best Regards,
    Anthony

  • 0 in reply to Anthony F
    Mastermind 7230 points

    Dear John Tucker,
    Dear Anthony Fagnani,

    Thank you very much for answer.

    I tell customer to advice.

    Best regard.

    Bob Lee.

  • 0 in reply to Bob Lee62837
    Mastermind 7230 points

    Dear John Tucker,
    Dear Anthony Fagnani,


    May I ask add question?
    My Customer use LM3495 and LM5022.


    TPS54360 same conditions use. (280kHz ± 10kHz at an external clock.)


    In this case,
    LM3495 and LM5022 is it possible synchronization？

    If synchronization is possible,
    how much would be sweep range?

    Best regard.

    Bob Lee.

  • 0 in reply to Bob Lee62837
    TI__Guru**** 191445 points
    I am not familiar with either of those LM3495 or LM5022. You may need to make a new post to inquire about those parts.
  • 0 in reply to JohnTucker
    Mastermind 7230 points

    Dear John Tucker,

    Thank you very much for reply.

    I make new post.


    Best regard.

    Bob Lee.