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LM5041 frailty

Salah GRIM
Prodigy 90 points
Other Parts Discussed in Thread: LM5041

I've designed a DC/DC (current fed push push pull) converter: 12V input, 2 outputs (+100V/-100V),MAX power 100W
Recently, we assembled 11 boards. In this batch, on 3 boards the LM5041 doesn't work ! the other 8 boards work fine.

when the power convertert start up, the push-pull stage seem ok, but step-down stage don't start.
let me explain:
on those 3 boards:
VCC=10.7V
VCC=10.7V)
VREF (REF)= 5V
Push/Pull turn on (250KHz)
HD=LD=0V
*****
After replacement of LM5041 with a new one the converter work fine.
the converter provide the good voltage/ power
I burned the converter with 100W load for more than 5Hours and i had no slightest problem (Efficiency 94% with 100W load)

have you any idea for the origin of this issue?


FYN the marking number of our controllers is JM23AB/5041SD.
I see the similar issue in your forum (e2e.ti.com/.../1439812

Thank you

  • 0
    TI__Mastermind 40520 points
    Hello Salah,

    I will alert the appropriate team of your question, and they should be able to address your issue.

    Regards,
    Ulrich
  • 0
    TI__Expert 3200 points
    Hello Salah,

    I can only make some suggestions based on the information you provided.

    If I understand you correctly, since HD=LD=0 V, then this is indicating a fault state which can include Vcc under-voltage, Vin under-voltage, 2nd level current limit, or Thermal protection to name the key ones. I suggest you look at the VIN, VCC, SS, UVLO, and CS pins during your start-up time to make sure none of the protection thresholds are triggering. My opinion at this time is it is a min-max rating being violated on VIN, UVLO, or VCC since a replacement of the controller means the circuit works which makes me think there is a tolerance difference between controllers and I am assuming the controller you replaced is not damaged.

    If a controller you replaced is damaged, then we need to look for max ratings being exceeded or voltage spikes. But since you are able to operate a working converter for 5 hours makes me not think of this as a leading cause for your failures.

    Look at these nodes and then let's look at the data for next ideas.
  • 0 in reply to Brian Johnson96
    Prodigy 90 points
    Hello Johnson,

    Than you for your fast replay:

    I have make additional measures on the points that you recommended me.
    all voltages are Ok in startup mode :

    Vcc=10.7V
    UVLO=3.3V
    Vin=10.7V
    Cs=0V
    SS=4V

    I have the same voltages in others board , and i havn't any controller error (turn on correctly)!

    Can I send you my design and measurements by email ?

    how i can add pictures in my replay ?

    Regards, Salah
  • 0 in reply to Salah GRIM
    TI__Expert 3200 points
    Hello Salah,

    Send your design/schematic/waveform captures/etc. information to b-Johnson@ti.com. We are getting ready to go on the US holiday break so my response may be delayed.
  • 0 in reply to Brian Johnson96
    Prodigy 90 points
    Hello Johnson,

    Happy Thanksgiving
    I sent my design/ waveform to your mail adress

    Regards,
    Salah