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LMR14020SEVM: Question about the LMR14020SEVM

user6094191
Prodigy 50 points
Part Number: LMR14020SEVM

Dear Texas Instruments E2E Suport,

Hello. I'm Yoshishige Tamura of IES corporation.

I have purchased the LMR14020SEVM and I'm trying to evaluate that for installing to our board.
but I have a few quesions for LMR14020SEVM.

The following questions are based on page 6 of the LMR 14020 SEVM User's Guide.

1. I'd like to omit the C10 and C11.
   Can the C10 and C11 be omitted? :I would like to omit the parts.

2. I would like to change the capacitor C8 0.027μF to a 0.022μF capacitor.
   :because we hard to get a 0.027μF capacitor.
   Does it work without any problems to change?


3.I don't see the point of the testpin TP7 is mounted. What is that for?

I look forward to hearing from you soon.
Yours sincerely,

Yoshishige Tamura

  • 0
    TI__Expert 4720 points

    Hi, 

    please send email to andy.chen@ti.com, the AE of this device.

  • 0
    TI__Mastermind 27045 points

    Hi Tamura,

    1. C10 and C11 are important capacitors for input bypassing, if there are other ceramic capacitors installed on your board and placed close to LMR14020SEVM input terminal, then C11 can be omitted and change C10 to 2.2uF 50V.

    2. It's OK to change C8 to 0.022uF if output voltage below 5V.

    3. TP6/7/8 are test point for measuring loop response, no impact on circuit normal operation.

  • 0 in reply to Andy Chen
    Prodigy 50 points

    Hello Andy,

    Thank you for answering my questions.
    If you don't mind ,there are two more things I would like to ask you.


    1. I would like to change R7 and R5 to 54.0kΩ resistance, and change R6 and R8 to 9.53kΩ resistance.
       :Does that mean the output +5V divide 0.75V?
       Does it work without any problems to change?

    2.The switching cycle of #1 and #8 has been shortened by changing parts.
      The parts are changed as follows,

    -Omited C10 and C11 :Following your advice,I will back to the original.
    -Changed the 0.0022uF to 0.0027uF.
    -Changed R7 and R5 to 54.0kΩ resistance, and change R6 and R8 to 9.53kΩ resistance.

    Could you tell me what caused it?
    I will attach a document of measured waveform.

    Best Regards,
    Yoshishige Tamura3250.waveform.pdf

  • 0 in reply to user6094191
    Prodigy 50 points

    I’m sorry for the mistake in the previous post.

    *Changed the 0.027uF to 0.022uF.

  • 0 in reply to user6094191
    TI__Mastermind 27045 points

    Hi Tamura,

    R7 and R5 to 54.0kΩ resistance, and change R6 to 9.53kΩ resistance,  do you program the output voltage to 9.2V?

    What's the load current during your testing?

    R6 9.53K is smaller than original 15.8K, it will slightly increase load current and cause switching freq close to 1.6MHz set by R3.

  • 0 in reply to Andy Chen
    Prodigy 50 points

    Hello Andy,

    >do you program the output voltage to 9.2V?

    No I don't, I program 5V.

    54.0kΩ = V out-0.75/0.75×9.53kΩ
    V out = 4.999V img-718171703.pdf

    >What's the load current during your testing?

    The load current is input valtage 24V :Output valtage 5V.


    >R6 9.53K is smaller than original 15.8K, it will slightly increase load current and cause switching freq close to 1.6MHz set by R3.
    OK.I will change to 15.8k.

    Best Regards,
    Yoshishige Tamura.

  • 0 in reply to user6094191
    Prodigy 50 points

    Hello Andy,

    >R7 and R5 to 54.0kΩ resistance, and change R6 to 9.53kΩ resistance,do you program the output voltage to 9.2V? 

    I just realized, I'm sorry,I make a mistake in grammar.

    I omitted R7. and I changed  R5  to 54.0kΩ resistance.

    Moreover,I omitted R8. and I changed  R6  to 9.53kΩ resistance.

    It will be programed  output voltage to 5V.

    Best Regards,
    Yoshishige Tamura.

  • 0 in reply to user6094191
    TI__Mastermind 27045 points

    Hi Tamura,

    How about your testing on LMR14020SEVM? any more question in your application?

    B R
    Andy