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LM3429-Q1: instruction on π filter for EMI optimization

Part Number: LM3429-Q1
Other Parts Discussed in Thread: LM3429, TPS92691, TPS92690, TPS92692

Usually how we design a π EMI filter and how to choose the size, value of the inductor and capacitors? Do we design the EMI filter before finishing the schematic design? And any related materials on the components selection to optimize EMI performance that I can take a look into? Below is the detailed application:

  • Application: High beam/Low beam
topology: LM3429 as a Boost controller
  • Input: 12V Battery Voltage
  • Output: 30V/1A
  • Switching frequency: 330KHz


  • Hello Ted,

    We have some app notes at:

    But you should always have some placeholders for differential mode and common mode filtering to be safe. If some can be cut out that's great, but EMI is very tricky and generally takes some experimentation. Make sure any common mode filtering you have has an SRF (or a good amount of impedance) past 108MHz for automotive. You can also check some of our newer EVMs and TI Designs using the TPS92690, TPS92691, and TPS92692. They are similar parts at similar power levels and have EMI filtering to pass CISPR 25 class 3 conducted emissions, so that might be helpful as well.