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LM5025A: Frequency synchronization

TISL
Expert 4075 points
Part Number: LM5025A

Dear Support,

In an Active Clamp Forward topology, with a solution such as our LM5025A, is it possible to change the switching frequency "on demand", to adapt the end application constraints? What would be the limitations?

It seems that we can set a fix frequency with RT pin, such as 160Khz for example, and then use the SYNC pin to be synchronized from 160KHz to 500KHz, or more. Is that correct? Can we also sync up to 1MHz?

Regards,

  • 0
    TI__Mastermind 31580 points

    Hi TISL,

    TI normally advise placing the RT frequency programming resistor close to the RT and ensuring it has a good connection to the AGND pin with no power signals flowing in that ground. The risk here is that adding any additional circuitry to the RT pin to dynamically adjust the frequency may also introduce noise into the system which may cause unwanted frequency variation or jitter in the system.

    From the datasheet the device can be synchronised to a frequency that is 20% below it free running frequency and can sync to a higher frequency with no restriction.

    The other option is disable the RT pin by connecting it to REF and using the sync signal as the master oscillator, see page 16, section 7.3.8

    Regards

    Peter

  • 0 in reply to Peter Meaney
    TI__Expert 4075 points

    Perfect Peter.

    Thanks for your feedback.

    If you don't mind, I'll contact you in private for additional and confidential questions.

    Regards,