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UC3846: The application issues of chips

Tonyx.wu
Genius 3915 points
Part Number: UC3846

Tool/software:

This time, during the production of WSM-400T, there was a problem of the large current being too small. The technical requirement was 400A, but the actual output was only 392A. Out of 500 units produced, 200 units were defective.

After research and development analysis, it has been confirmed that the issue is caused by an abnormality in UC3846. Currently, the initial analysis indicates that the output pulse width of UC3846 has decreased. This project is a 5 to 10-year-old one, and the design has not been changed. However, the client has a package of materials purchased from the spot market. Could you please help check if there are any design issues? Or this material involves PCN changes

  • 0
    Genius 3915 points

    Basic situation description.docxFA FROM.docxsummary-CPR251125999.pdf

    Add some attachments for your reference, including the records of the FA application

  • 0 in reply to Tonyx.wu
    TI__Guru 73215 points

    Hi,

    What do you mean  "the client has a package of materials purchased from the spot market."? What is the spot market? Is it due to the spot market from where do you confirm the devices are from TI?

  • 0 in reply to Hong Huang
    Genius 3915 points

    1)ARROW has shipping records, such as in the picture.

    2) Before, when there was a shortage of stock, the customer bought a pack of ready-made items from the market. I was worried that a small amount might be mixed in ARROW's shipment.

    3) The current client's request is to conduct a FA analysis. Please first help check if there are any issues with the schematic design and other aspects. I still need to communicate with the quality department about the FA analysis. It's quite urgent. Please do it as soon as possible.

  • 0 in reply to Tonyx.wu
    TI__Guru 73215 points

    Hi,

    If this circuit was used on in the past, then the circuit is ok. I can do a circuit review if the circuit is a new design. Please help to clarify. 

  • 0 in reply to Hong Huang
    Genius 3915 points

    This circuit was used before and has been in continuous use for a long time.   There were no issues before and no changes were made.   However, when using the latest version chip, the output current would decrease, and the proportion was quite high.   I thought it was related to PCN, but I found that there has been no PCN-related change for this material recently.   If you have no other suggestions here, I'd like to apply for FA analysis first.

  • 0 in reply to Tonyx.wu
    TI__Guru 73215 points

    Hi,

    It can be due to the max duty cycle with min value smaller. You can measure the duty cycle at operation when the current starts to decrease and compared to a good one. If you find the duty cycle cannot be kept, but still in the datasheet range then it is your design not enough margin. If the duty cycle is much smaller than the datasheet specs, then it is likely a device issue then you can request FA.