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LM5017: OUTPUT ACCURACY

Erin Zhang
Prodigy 130 points
Part Number: LM5017

Hi,

My customer want to know how to improve the output accuracy of LM5017.I want to know how to solve this problem

Thanks and best regards

  • 0
    TI__Mastermind 26340 points

    Hello Erin,

    We will be happy to assist, can you please provide me with the details of the issues the customer is seeing?  If possible providing a schematic would be really helpful.  Also please can you provide some commentary on where exactly customer is seeing the issue?  for example, Is it when the supply is loaded?  What is the discrepancy in output voltage regulation the customer is seeing? 

    Thanks in advance,

    kind regards,

    David.

  • 0 in reply to David Baba
    Prodigy 130 points

    Hi David，

    My customer found  the line regulation of LM5017EVM is not satisfied. Do your have some good idea for this problem?

  • 0 in reply to Erin Zhang
    TI__Mastermind 26340 points
    Hello Erin,

    I do notice that you have C2 installed? This does not need to be installed with Type III ripple injection. Please have them remove C2 and retest to see if line regulation improves.

    kind regards,

    David.
  • 0 in reply to David Baba
    Prodigy 130 points
    Hello David,
    We have removed C2 but the line regulation didn't improve .
    Thanks and best regards
  • 0 in reply to Erin Zhang
    TI__Mastermind 26340 points

    Hello Erin,

    Please can you provide me with your customers specifications and inductor used in the schematic above? Also can you provide me with the details of how much the output voltage is varying?  Thank you.


    Kind regards,

    David.

  • 0 in reply to David Baba
    Prodigy 130 points
    Hi David

    the Vout of the LM5017EVM changes from 9.98V to 10.5V, when the Vin changed from 12v to 30V . They want to know how to keep the Vout below 10.2V. They uesd the 220uF inductor for EVM test. And they want to know whether a smaller inductor will infiuence the stability.

    thanks a lot for your kindly help.
  • 0 in reply to Erin Zhang
    TI__Mastermind 26340 points

    Hello Erin,

     

    Yes the Inductor most certainly will.  The DCR of the inductor in addition to the ripple current in the inductor also will have an effect, which is why it would be useful to get a part number?   My suspicion is that you are injecting too much ripple voltage into the feedback node.  If you are using Type III, increasing Cr (C6) will reduce the amount of ripple voltage at the feedback node.  Reducing the inductor value will increase the ripple voltage.  I do not recommend increasing the inductor value, but rather reducing the amount of ripple by Adjusting Cr accordingly. Can you try C6 = 10nF?

     

    Thanks.

     

    Kind regards,

     

    David.

  • 0 in reply to David Baba
    Prodigy 130 points
    Hello David,

    Thanks a lot.We change the C6 to 10nF and the output accuray improved. But the load transient is not so good. Could you please help me look into this problem?

    best regards,
    Erin
  • 0 in reply to Erin Zhang
    TI__Mastermind 26340 points
    Hello erin,

    Do you have a scope plot of the load transiet of the output voltage?

    Thanks.

    David.