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LMZ10501: The probability of Vout's soft start time too long and the output voltage wrong

Feng bin Su
Expert 7590 points
Part Number: LMZ10501

Hi team,

My customer use LMZ10501  but it face some issue that would like to consult with you..The schematic is as below.

There are several assembly board that have the below problem after start up. 

Normal:(CH1:EN, CH2:Vout)

Issue1: 

It need to take a lot of time (several seconds) to be operating voltage after starting up.

Issue 2:

Output voltage is unnormal after strating up.

.

We have done some resoldering for the assembly board by hot gun air and the behavior will change into different case with possibility.

May I have your comment and suggestion to prevent the failure case happening possibility ? Thank for your help.

  • 0
    TI__Mastermind 47060 points

    Hi Feng,

    The schematic looks okay. It follows the typical schematic for a 1.2Vout application seen in Figure 17.

    I've listed out a few questions I have to help better understand the setup:

    1. What is the loading current in your application?
    2. Can your provide scope shots of VCON, VOUT and IOUT as well?
    3. What is your solder profile?
    4. Can you confirm that during resoldering, there is enough solder paste and coverage of each pin?
    5. Can you describe how the behavior changes after resoldering (VOUT stability, VOUT settling time, etc.)?

    From your description of the resoldering, it sounds like behavior changes which may indicate an affect of either solder or temperature. 3.3V to 1.2V is a typical application and the schematic your customer has does not raise any initial concerns.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Mastermind 47060 points

    Hi Feng,

    Can you provide comments and an update on the progress of the failure mode?

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Mastermind 47060 points

    Hi Feng,

    I haven't heard back from you in a while. I assume you were able to resolve your issue on your end. Because of this I will be closing the thread. If you have additional questions or comments please reply to this message and the thread will reopen for further troubleshooting.

    Regards,

    Jimmy