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TPS63070: EMC problem in PWM Mode

Dominik Eschenmoser
Prodigy 20 points
Other Parts Discussed in Thread: TPS63070, TPS63070EVM-693

Hi 

We are using a TPS63070 in our Design in forced PWM mode.

Vin 3.3V to 12V Normal Operating 9V 

Vout 5V 

We detected a strong 2.5MHz emission over our Inductor L1 @9V Vin. 

Our Internal ADC converter is massive disturbed from the 2.5MHz emission. 

So we made the same test with the reference design kit TPS63070EVM-693 and had the same issiue over the Inductor. 

Is there a way to reduce the EMC emission of the switcher  in our design and on the reference design kit ? 

  • 0
    TI__Expert 8420 points
    Hi Dominik,

    The device has a switching frequency of 2.5MHz, therefor it is expected to measure the switching behavior of 2.5MHz across the inductor on the EVM. This is shown on Fig 29 and Fig 30 of the datasheet.

    This could be mitigated in your application by optimizing the layout of your design and adding appropriate filtering.
  • 0 in reply to Sabrina
    Prodigy 20 points
    Hi Sabrina.

    We used the exactly design as it is on the reference design kit. Is there no other way to reduce the emission of the switcher?
    On this part we have some margin to change the design or assembly. On the other part where the irradiation of the switcher is, there we can't easily change the design.
  • 0 in reply to Dominik Eschenmoser
    TI__Expert 5425 points
    As Sabrina already pointed out, the 2.5MHz rectangular waveform you can measure at the inductor is intrinsic to the operation of this device. If you can measure it there it basically means that the converter is operating properly. You will find similar waveforms in any inductive DCDC converter.
    The application design, mainly the PCB layout, just needs to be done in a way that those waveforms can not interfere with other parts of the circuit. If you send me your layout I may be able to give you hints on how to reduce the cross coupling.