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LM5122: Question about sync

Austin Do
Expert 3335 points
Part Number: LM5122

Tool/software:

Hello team,

Is it possible to set "fsync, free running with RT resistor"?

The customer needs the two same switching frequencies from RT resistor and external sync. 

Best Regards,

Austin

  • 0
    TI__Mastermind 30410 points

    Hi Austin,

    Thanks for using the e2e forum.
    LM5122 is only capable of the four settings that are described in the table.

    Only Master1 settings allows the free running oscillator frequency with Rt. If they want to achieve the same frequency with an external sync, so they can switch between Rt and sync generated signal, they would need an external sync signal with twice the frequency.

    If they use Master2 configuration, they cannot use the Rt anymore.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    TI__Expert 3335 points

    Hi Niklas,

    Is it okay to set the external sync frequency as 1.2MHz and Rt as 600kHz? 

    In datasheet, it seems fsync is limited by 1MHz.

    Best Regards,

    Austin

  • +1 in reply to Austin Do
    TI__Mastermind 30410 points

    Hi Austin,

    The switching frequency recommendation of max 1MHz applies for the actual switching frequency.
    Is see no limitation for the external sync signal, so it is possible to apply a 1.2MHz signal at the sync pin to create an actual fsw of 600kHz in Master1 configuration.

    Best regards,
    Niklas