• State TI Thinks Resolved
  • Locked Locked
  • Replies 9 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 2654 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM46002: power supply stops working after 2 month

Karl Jahn
Prodigy 80 points
Part Number: LM46002

We have a power supply designed with the following parameter

Vin = 7,5-30 VDC , Vout=5V Iout_min=50mA, Iout_max=1A

The design works properly. Now we have 2 of 1000 units back, where the power supply stopped working after ~2 months.

We measured the following:

Vin=7,5V, V_enable=3,7V, Vcc=2,4V, Cboot=2V, SS/Trk=0V, RT=2,1V, Sw0V, Vbias=0V 

The only way we could "restart" the power supply, was when we applied 3,2V (with an external supply) to Vcc-Pin just for a second.
Then the power supply works as designed. But when we disconnect the V_in => the power supply won't start again until we put 3,2V to Vcc for a short time.

Are there any suggestions what could cause this issue?

br, Karl

  • 0
    TI__Mastermind 23845 points
    Hi Karl,

    During the 2 months is there any power cycling on the VIN that might causing the output to be discharged to VIN or in other words is there a condition where VIN < VOUT?
    Also is the failure happens at room temperature?

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    Prodigy 80 points
    This failure happens also at room temperature. Changing the temp with a heat gun or ice spray does not change the behaviour.
    I can't think of a condition where Vout>Vin
  • 0 in reply to Karl Jahn
    Prodigy 80 points

    I have checked the Vcc start up

    yellow Vcc Pin
    purple V_in +8V
    blue V_out +5V

    good power supply:

    not working power supply: 

    applying 3,2V to the Vcc Pin of not working power supply

  • 0 in reply to Karl Jahn
    TI__Mastermind 23845 points
    Hi,

    If you remove the external supply to the VCC will the part still operates?
    Also is the VCC capacitor working ok with it's rated voltage? What happened if you substitute the VCC capacitor? That is just to double check that the capacitor is not leaking and causing VCC to drop.
  • 0 in reply to Arief Hernadi
    Prodigy 80 points

    If you remove the external supply to the VCC will the part still operates?
    Yes, until I unplug the complete system and restart it.

    What happened if you substitute the VCC capacitor?
    I replaced the capacitor already => no change in the behaviour.

    The Vcc is quite strong. I put an external resistor as a load to VCC (just for a test). When Vcc was at 3,2V an the IC was working, a resistor with 10 Ohm did not change much at Vcc (I applied the resistor just for a few seconds). When Vcc was at 2,4V (IC not starting), the votage at Vcc dropped when I put an external load on.

    br, Karl

  • 0 in reply to Karl Jahn
    TI__Mastermind 23845 points
    Hi Karl,

    Thank you for the experiment, do you have an evaluation module such as this one?
    www.ti.com/.../lm46002pwpevm

    If yes, would you mind testing the not working IC on the evaluation module and see if it behaves the same?
    I can send you one if you don't have the evaluation module.
    Just give me your address and email/contact information so that i can send it to you.

    If the IC still fail, then you can send the IC back to the factory for further failure analysis. Do you have a TI representative that works with you?

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    Prodigy 80 points
    Thanks for the offer.
    I would like to send it back to the factroy.
    I do not have an direct TI representative. I'm from Austria
    Can you send me an adress, where to send the package?
    br, Karl
  • 0 in reply to Karl Jahn
    TI__Mastermind 23845 points

    Hi Karl,

    Attached is the FA form that our customer normally fill to have an FA request. Would you mind filling this up and send it to my email address? 

    arief.hernadi@ti.com and the address to ship will be under my name at

    Arief Hernadi

    2900 Semiconductor Drive

    Santa Clara, CA

    95051

    USA

    I will route the form to the QA group in here

    6644.fa_request.doc

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    TI__Mastermind 23845 points
    Hi Karl,

    After speaking with the QA manager, he was suggesting to contact the distributor where you get the part from and they can use the proper channel to fill up the FA request form officially.

    Thanks
    -Arief