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UCC256403 : Problems with the emi test under low load.

Matthew85
Prodigy 90 points
Part Number: UCC256403

When performing the emi test at low load.
The value between the frequencies between 0.15MHz and 0.5MHz is large.
There is no problem when the load is high.
Is it correct way to modify the LL/SS pin to solve this problem?

  • 0
    TI__Genius 9790 points

    Hi, Matthew

    EMI is worse at light load is because of hard switching at light load, you may need to :

    1. Increase BMTH by modifying LL/SS pin

    2. if external capacitor is added on Drain to Source of LLC MOSFET, you may need to decrease the capacitance and use MOSFET with smaller COSS.

    3. decrease magnetic inductance Lm is also helpful.

    Yunsheng