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Original question:

LM25149-Q1: EMI data

LM25149-Q1: Disabling Spread Spectrum (DRSS)

Darius Babar
Prodigy 40 points
Part Number: LM25149-Q1

Tool/software:

Hi,

I have a few questions regarding the LM25149-Q1.

Is DRSS disabled by placing a 24,9k or 29,9k ohm resistor at CNFG? The application examples in the datasheet show a 24,9k ohm resistor and the table of configuration modes says 29,9k. Which one is it?

Also, is there a way to disable and enable DRSS more freely? The datasheet says "DRSS is disabled when an external clock is applied to the PFM/SYNC pin". How do I apply this in practice? 

  • 0
    TI__Guru 55832 points

    Hi Darius,

    My understanding is that any resistance in the 24.9k to 29.9k range will work - I will confirm this and get back to you. Also, you can apply a synchronization clock signal at the required switching frequency, which effectively disables DRSS and forces fixed-frequency operation based on the applied clock.

    Regards,

    Tim