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LMQ61460-Q1: Best location for EMI filter

Art Mecina
Genius 16585 points
Part Number: LMQ61460-Q1
Other Parts Discussed in Thread: TPS2660, LMQ61460

Hello Guys,

Good day.

Our customer is working on a low EMI medical device. They would like to use the LMQ61460 as their DCDC regulator for 24V down to 5V and the TPS2660 to provide input protection for both reverse polarity and inrush. They would like to include an EMI filter on the input to reduce emissions. They would like to know what the recommended location for the EMI filter would be for best performance. They are deciding if it should be before or after the TPS2660.

I found from this application note that for best performance it should be after the TPS2660:https://www.ti.com/lit/an/slyt707/slyt707.pdf

If possible could you explain why this is the more effective location than before the TPS2660? Is it just simply to make the best use of the TPS2660 to protect the components of the filter from external transients?

Also, are there any special considerations for if the TPS2660 suddenly cuts the current in an overcurrent scenario? As the filter has inductive components. I guess an output diode reverse connected to ground would stop this from being an issue if the voltage spikes below ground in a short circuit.

Thanks and regards,

Art

  • 0
    TI__Guru 65775 points

    Hello

    The best place for the EMI filter is near the input of the LMQ61460, since you want to stop the EMI as close as possible

    to the EMI source.  

    You can use a reverse connected diode if you wish.

    Another best practice is to damp the EMI filter with an Al. electrolytic capacitor or with a ceramic capacitor in series with a small resistance.

    See application note SNVA489 for more information.

    Thanks