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TPA3251: Implications of using a bootstrap resistor to slow the OUT node rise time

Part Number: TPA3251
Other Parts Discussed in Thread: TPA3245

Hello,


What are you thoughts on placing a small resistor in line with the bootstrap capacitor to slow the rise time of the OUT nodes to help reduce the >100MHz EMI that can from high frequency switching.

  • Hi Ryan,

    The bootstrap capacitor value is optimized for proper function. TI does not recommend using a different value or placing a small resistor in line with the bootstrap.
    There are many other ways to deal with EMI, including the snubber networks that we include on the EVM schematic, using shielded inductors, and proper PCB layout. We are always happy to do Layout and schematic reviews or make general recommendations to improve EMI performance. We have advised many of our customers when they are testing for CISPR-13 and have never had any problems.

    best regards,
    -Steve
  • Hey Ryan, one other thing occurred to me as I was thinking today. The TPA3251 does have a built in feature that softens the edge of the PWM but this feature only functions when PVDD is 36V.

    similarly the TPA3245 has this feature but it only functions when PVDD = 31.5.