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LM3492 Vin Ripple Susceptibility

Ruwan Subasinghe
Prodigy 110 points
Other Parts Discussed in Thread: LM3492

Hello,

I am working on a LED lighting board design which is designed to be powered by a wall-mount SMPS. I've designed the LM3492 regulator to operate with Vin between 9-16V, almost exactly following the Evaluation Board reference design covered in AN2056.

Our options for 12V switch-mode power supplies have ripple+noise values of 100~200 mVpk-pk. Unfortunately the switching frequency of the adapters are variable/unknown, but I assume the low frequency component of the ripple lies in the 20kHz-2MHz range. 

My question is how susceptible is the driver circuit using LM3492 to up to ~200mVpk-pk ripple on Vin? What effects should I be on the look out for during testing and what can be done to reduce negative effects?

Thank you,

Ruwan

  • 0
    TI__Mastermind 25500 points
    The LM3492 should handle it just fine. The internal circuitry is run off a fast linear regulator and that ripple has no good way to get through the inductor. If you are still concerned you can simply increase the input capacitance or you could add a small L and C to form a pi filter with the input capacitor. If there are EMI standards you need to meet that filtering will likely be more than enough anyway.
  • 0 in reply to Clinton Jensen
    Prodigy 110 points

    Great to hear. We will have to meet EMI standards, and we will be testing the design thoroughly before production. I just wanted to get an intuition about how LM3492 reacts to ripple.

    Thanks for your help,

    Ruwan