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LM3429: LED driver make a lot of noise on FM-radio

Jejomar Ildefonso
Expert 8590 points
Part Number: LM3429

Hi Team,

I've made a LED buck-boost (BB) driver based on LM3429. It's for automotive lighting, so Vin = 9-14.5 V, LED string consist of 10 white leds. Vout is about 30V, Iout=1.3A. All components were calculated according to LM3429 datasheet for BB topology. All datasheet recommendations for PCB design were also used. So, prototype PCB has factory execution.

During the tests there is a lot of noise on FM frequency, however driver works properly at everything else. Noise on FM radio comes from induction - it sounds different in speakers when touched. But seems like it comes from all high frequency circuit with MOSFET and LM3429. Currently we have no idea on how to remove this noise, where could be our mistake? Led string is separated from the LED driver into a separate cooper board, wire length is about 25-30 centimeters.

Attaching our schematic, PCB, operating conditions and component values for reference. Thanks in advance!


Kind Regards,

Jejomar















  • +1
    TI__Genius 17640 points

    Jejomar,

    What you are describing is EMI and high frequency radiation that is picked up by the radio.  EMI is a total system design that will need housing to shield and prevent unwanted EMI noise from the regulator from getting out.  Beside the housing, you might also need EMI filtering for high frequency both on the input power and on the output stage.

    Thanks Tuan