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LM5118EVAL: LM5118EVL

Ali Bakhtiyari75
Prodigy 40 points
Part Number: LM5118EVAL
Other Parts Discussed in Thread: LM5118

Hello All,

I bought the LM5118 evaluation board and now I am trying to get a (12 V at 1 A) output.

I connected a resistor load at the output and apply the voltage from 5 to 15V to the input.

The problem is with the input voltage below 10 V the EVB does not work ( I can hear some noise from the inductor !)

I am also sure my power supply can deliver above 5 Amp.

According to the datasheet of the evaluation board (page 4: Note that this design uses a current limit value to guarantee a full 3 A of output current at a minimum VIN of 5 V.) I should be able to get the output voltage 12v@1A when the input voltage is 5 volts , but by some reason it does not work.

Please kindly help me on this issue.

King Regards,

Ali

  • 0
    TI__Mastermind 21720 points
    Hi Ali,

    First, has anything been modified on the EVM? When you say doesn't work can you give me more detail? Is the output voltage not regulate or is there something else going on?

    Please confirm that your input power supply is not limiting. It is possible that there might be current limit set lower than the maximum of the supply. Also take see if the input voltage is oscillating, this might indicate some impedance mismatch between boost mode operation and the power supply.

    If you can provide any waveforms this can be helpful.

    Thanks,

    Garrett
  • 0 in reply to Garrett Roecker
    Prodigy 40 points

    Hi Garret,

    I just found the issue and now EVB works as it should.

    The input voltage was oscillating during the boost mode and as you mentioned it looks like a impedance mismatching.

    Thanks for your quick reply and help.

    Ali

  • 0 in reply to Ali Bakhtiyari75
    Prodigy 40 points
    Dear Garret,

    By the way , could you please kindly guide me if there are any reliable methods to protect the input voltage from this kinds of mismatching?
    Finally I will use LM5118 in my design which is in automotive industry and the power will provide with the long cable to the system.

    for sure I will use the standards filters for the input voltage, but if there are any other consideration , please kindly let me know.

    King Regards,
    Ali
  • 0 in reply to Ali Bakhtiyari75
    TI__Mastermind 21720 points

    Hi Ali,

    There are a lot of application notes available on TI.com that walk through EMI filter design. Below is a really good example of EMI filter design. I talks about properly selecting components so no oscillation occur.

    http://www.ti.com/lit/an/snva489c/snva489c.pdf

    Let me know if you have any more questions.

    Thanks,

    Garrett

  • 0 in reply to Garrett Roecker
    Prodigy 40 points

    Hi Garrett,

    Thanks for the link and your support.

    for sure I will bother you with my questions in future, if face with problems.

    King Regards,

    Ali