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LM5143-Q1: Ripple Issue

Ganapathy Raman
Prodigy 130 points
Part Number: LM5143-Q1
Other Parts Discussed in Thread: LM5143

We are testing a DC to DC converter that converts 50V to 5V, with a load of 30A, utilizing the LM5143 interleaving dual buck converter. During our testing process, we have observed a ripple at 10KHz when examining the output voltage in RF Spectrum. However, when we analyze the same output voltage using the Scope, we are unable to detect any ripple.

How to effectively identify and rectify this ripple issue. Any insights or recommendation to resolve it?. Additionally, if there are any specific troubleshooting steps or tools we should use to address this matter, please kindly advise.

  • 0
    TI__Mastermind 29380 points

    Hello Ganapathy,

    please check if you have spread spectrum enable.  Also turn off all other switchers on the same board as it could be beat frequencies.  Also put persistence on the scope, there may be slight, but acceptable jitter on the switch node.  could be any one of these items.

    Hope this helps.

    David.

  • 0 in reply to David Baba
    Prodigy 130 points

    Thank you for your reply.

    As per datasheet, if we disable the DITH pin by connecting to VDDA is only for start up? Or for continuous?

    Additionally, we use LM5143 only for buck converter purpose, no other switchers in our circuit.

  • 0 in reply to Ganapathy Raman
    TI__Mastermind 29380 points

    Hello Ganapathy,

    by connecting DITH to VDDA disables Spread spectrum.  The disabling of spread spectrum occurs during start up and remains disabled throughout operation, this is what the description is saying.

    Hope this helps.

    David.