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BQ24133: change BTST RC value for EMI

KANE SUNG
Prodigy 210 points
Part Number: BQ24133

Dear Sir,

We're using BQ24133 on our product, but EMI fail when charging current >1.1A.

EMI improved after change R156 to 10ohm and C174 to 470pF.

Any side effect if we apply above change?

Thanks.

Best Regards,

Kane

  • 0
    TI__Expert 8690 points

    Hi Kane,

    Leave C174 as 47nF, as this would be needed to maintain the voltage above 3V or 4V (VBTST_REFRESH) for each cycle.

    The resistor will not cause any problem, it should improve your EMI results. You can also use an RC snubber on the SW node to slow down the edges as well if you still have EMI issues. A better approach to reduce EMI is to place the inductor very close to the SW output, place the sense resistor close to the inductor and place the output caps very close to the sense resistor. The smaller the power stage loops, the EMI gets reduced.

    Regards,
    Steven