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  • TI Thinks Resolved

TPS54290: Not getting Out2 as expected

Part Number: TPS54290

Hi,  We are using TPS54290 in our design and using it as Dual output source ( 1.8V and 3.7V respectively) .

PVDD1 and PVDD2 are shorted and fed by 12V supply.

Default EN1 and EN2 are pulled down. 

After turning on input PVDD1=PVDD2 = 12V . We are getting Out 1 around 1.48-1.9V  on 5 boards we tested( should be 1.8V as R1 /R2 at FB1 are 20K/16K) .

But major issue issue is with Out 2  . we are getting around 1.77V - 2V range on 5 boards we tested.  (should be 3.7V as R1 /R2 at FB2 are 33K/9.1K) .)

Is there any sequencing required for EN1 and En2  ( EN2 should come before EN1) in case when we have PVDD1 and PVDD2 tied together?

 

  • In reply to BHUPENDAR SINGH:

    At this point, I am just trying to get you up and running. Please use 12 V as your input for now.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to JohnTucker:

    Thanks John!
    After replacing the compensation component values as you suggested TPS54290 s up now. It is working with both 5v and 12V input supply.
    But still we really have no clue that how these new values are selected as when we calculated the values as per datasheet , we got different values and TINA spice model was working as expected with those values while simulating our design. Just for our knowledge can you please see the attached sheet and let us know here we went wrong while calculating the values as it will surely help us in any future design.
  • In reply to BHUPENDAR SINGH:

    I am pleased that my recommendation worked.  Sometimes power supply design is a mixture of both science and art as I did not use any equations to design the compensation network.  I don't see your attachment.  If you can provide it I may be able to give you some feed back.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to JohnTucker:

    0743.slum164 (4) - autosave 17-12-07 10_55.TSC8473.DC_DC_Buck Regulator_Components_Calculations_updated.xlsxSorry i didn't mentioned correctly, it was attached in one of my previous reply. I am attaching it again here.

  • In reply to BHUPENDAR SINGH:

    The TINA model you attached is for transient response and The Excel file will not open. Since the values I provided previously are working properly, I will close this as resolved.

    Thanks,

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to JohnTucker:

    Hi John,

    Yes with the  value you provided, it is working. But we wanted to know where we went wrong in calculating the compensation network components values and how these values arrives.

    It will be really helpful if you can go through the excel and see if we did something wrong. We couldn't find it from our end . And if we leave it now,  it can again be repeated in future design too if not corrected.

    Thanks & Regards,

    Bhupendar

     

  • In reply to BHUPENDAR SINGH:

    Bhupendar,

    I have reviewed the spreadsheet you sent.  It had an invalid character in the file name that prevented me from opening  it, but renaming fixed that.   I went thru every calculation in detail and did not find any errors.  I also used the resulting component values in pspice.  Pspice predicts output 1, Fco = 57 kHz, PM 36 deg.  Output 2, Fco = 68 kHz, PM = 13 deg.  Both of those are low especially output 2.  As I may have stated previously, we inherited support for TPS54290 from another group, so I do not know who derived those compensation equations and spreadsheet.  They most likely work well for some scenarios, but not for your case.  I will note this issue to our management to see if someone can be assigned to update it.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

  • In reply to JohnTucker:

    Thanks John!

     Appreciate your support on this issue.

    It will be great if you can route us to the right contact who can help us to find the right way to calculate compensation values for TPS54290.

    Thanks & Regards,

    Bhupendar

  • In reply to BHUPENDAR SINGH:

    John,

    Thank you for supporting Bhupendar on this issue. He is working on my board design and the TPS54290 looked like an ideal part for our prototype but we will not be able to use it for production or any future design if we cannot figure out how to calculate the correct values for the compensation circuit. Please let us know if you can find the right person at TI to figure this out.

    Thanks,
    Dave Urban
  • In reply to David Urban:

    Hi Dave,

    My group inherited this part during a re-org. I would like to fix all this, but it is not a simple task to reverse engineer those equations, re work them, then validate the new design procedure for several corner cases, rewrite the excel tool and update the datasheet. My queue for a project of that scale is full up at the moment. As I may have commented earlier, I personally use and recommend pspice modeling for compensation design, which is supported for TPS54290. Will that work for you? I can arrange a tutorial if you like. Let me know, I can set something up.

    Best  Regards,

    John Tucker

    BSR-CCP LV/MV DC/DC Applications

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