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WEBENCH® Tools/LM5017: Problem to 5017

Ravi Shidore
Prodigy 135 points
Part Number: LM5017

Tool/software: WEBENCH® Design Tools

Hello David Baba,

I am sending waveforms of switching. Please find the image.

  • 0
    TI__Mastermind 23845 points
    Hi Ravi,

    Do you know which post that you have for the initial problem?

    Thanks
    -Arief
  • 0
    TI__Mastermind 40040 points

    The Switch node waveform looks fine to me.  It also looks stable.  The likely reason why your part is failing is due to an overshoot at the input when starting up or making a fast transition of the input voltage.  As I mentioned previously, should place a 2.2uF ceramic very close to the input to the device (Vin and Gnd)  and also place sufficient damping at the input supply to your board where the power connects, to avoid overshoot of the input voltage due to parasitic inductances/ringing.  I recommend trying a 33uF electrolytic with an ESR of ~0.5ohm as a damping cap.  I hope this helps with your issue?

     

    Kind regards,

     

    David Baba.

  • 0 in reply to David Baba
    Prodigy 135 points
    Dear Mr David Baba ,
    Pls refer enclosed exhibits in which we have captured various waveforms on a dual trace oscilloscope. Generally the channel/trace 2 in blue color is SW node wave form and channel 1 is inductor current waveform.
    Exhibit1:::  these are when V in is 36 V . Both the waveforms seem to be ok.
    Exhibit 2,3,4::  these are when Vin is 48 V . You may see intermittent spike in Inductor current waveform .( inductor saturating)
    After repeated  power on's ic failed . This time output pin short . In all previous case it was input pin short.
    Exhibit 5&6 ::: waveforms when Vin is 60V and 72V . The inductor current waveforms are still bad.
    Exhibit 7 ::: this is for reference and comment only . This is input current from 72 V waveform . The freq is different , the current is different . We are unable to understand this .
    Please reply...
    Thank you...

  • 0 in reply to Ravi Shidore
    TI__Mastermind 40040 points
    Hello Ravi,

    What inductor are you using? Do you have a part number please? I am assuming your load is running at 1.2A? Please can you confirm this too?

    Thanks and kind regards,

    David.
  • 0 in reply to David Baba
    Prodigy 135 points

    Hello David ,

    We are not using any standard part as inductor . We have wound the inductor on ferrite dumbbell . 
    We are using a similar inductor for a Power supply using LM 2576 .
    But looking at  the waveforms do we conclude that the inductor is saturating ? Or what could be reason for such failure .
    We will measure and inform you the load tomorrow.  We are using this for our prestigious product " Battery Equaliser " . 
    We are very much concerned today that we may loose the business because of this failure ...
    Ravi Shidore
  • 0 in reply to Ravi Shidore
    Prodigy 135 points
    Can you give me your contact number so I can call you.
    Now I am in USA so I can easily contact you.

    --Ravi Shidore
  • 0 in reply to Ravi Shidore
    TI__Mastermind 40040 points

    Hello Ravi,

    It does look as though the the inductor is saturating, also I do not recommend using an open core inducor with a COT control architecture because COT uses a feedback comparator, in contrast to an Error Amplifier with a relatively low BW as in the case of the LM part you mentioned.  I recommend using a shield inductor with COTs  I suggest replacing with a shielded inductor with specs we know are suitable to determine for sure,  its the inductor.

    Kind regards,

    David.

  • 0 in reply to Ravi Shidore
    TI__Mastermind 40040 points
    I am happy to discuss in more detail with you Ravi, please email me so I can provide you with details.

    David.Baba@ti.com.

    Thanks and kind regards,

    David