This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS54061: Can 5~10 ohm resistor be inserted between BOOT terminal and external boot cap to reduce EMI noise?

Part Number: TPS54061

 Hello guys,

 One of my customers is considering using TPS54061 for their new products.

 They want to get a answer of the following question for case of EMI problem happened.

Ques.  Can 5~10 ohm resistor be inserted between BOOT terminal and external boot cap to reduce EMI noise generated by fast SW node transient speed?

            Is there any problem of TPS54061 function to insert the resister?

 Your reply would be much appreciated.

 Best regards,

 Kazuya. 

  • Hi Kazuya,

    It's generally OK to use 5~10 ohm as Rboot to limit turn-on speed, however you need check the SW and BOOT waveform at condition of maximum duty cycle(for Vin-min to Vout-max) at required switching freq, the switching waveform should be stable and BOOT to PH voltage higher than 2.5V.

    B R
    Andy  

  •  Hi Andy,

     Thank you very much for the prompt reply.

     I understood and I will tell them to check the voltage between BOOT and PH when the ON duty is maximum.

     But could I ask you a few questions to your reply?

    Q1. You said that BOOT to PH voltage higher than 2.5V. I think TPS54061 has a UVLO which checks the voltage

          between BOOT and PH. Also the UVLO detection (or releasing?) voltage is 2.9V (typ) according to the device datasheet.

          Is it enough that BOOT to PH voltage higher than 2.5V. Or does the voltage need higher than 2.9V? Is 2.9V enough? 

    Q2. Do you have the maximum detection voltage of the UVLO?   

     Thank you again and best regards,

     Kazuya.

  • Hi Kazuya,

    Sorry the BOOT to PH UVLO is 2.9V, NOT 2.5V

    Q1: once BOOT UVLO is triggered, chip will stop switching immediately and start to refresh the Cboot till it is about 6V or equal to VIN (if between 4.7V~6V) 

    Q2: UVLO typical is 2.9V, no data sheet spec. for maximum value, you can use 3.8V as rough estimation.

    B R

    Andy

  •  Hi Andy,

     Thank you for your reply.

     I understood.

     Thank you again and best regards,

     Kazuya.