TPS54200: TPS54200 audible noise at PWM dimming

Terry Wu

Part Number: TPS54200

Hello Sirs,

We face an audible noise issue when using 500Hz 1.8V PWM input .

Vin is 12V

LED current is 250mA (Vref 100mV, Rsense is 0.39 ohm) . Trying to wire PWM signal to TPS54200 EVM also have same problem ... TKS !

Schematic as below ( Pls ignore boost-Cap mistake )

R255 is 4.7K , C388 is NC .

Many thanks !

0 Summer SU over 8 years ago

Hi Terry,

Could you help to where the noise from, inductor or cap?

Since I am out of office today, I am sorry I can't verify it in the lab.

Thanks!

Summer

0 Terry Wu over 8 years ago in reply to Summer SU

Expert 1680 points

Hello Summer,

Sorry that I can't make sure its inductor or Cap .. Do you know how to check ?

Datasheet suggest 4K filter for PWM dimming , will it be a problem ? TKS~

0 Summer SU over 8 years ago in reply to Terry Wu

Hi Terry,

Could you remove the filter in the PWM pin?

Thanks!

Summer

0 Terry Wu over 8 years ago in reply to Summer SU

Expert 1680 points

Hello Summer,
Only 4.7K ohm series into PWM pin. Need to remove it ? TKS~

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