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UCC12050: Found damaged upon power on in production batch.

Ketan Lakhera
Prodigy 30 points
Part Number: UCC12050

Tool/software:

Hello, 

I have been using UCC12050DVER as a 5V isolated power supply to power 2 opto-isolators namely TLP2395. Following is the schematic diagram.

However, we have been seen production issues where this IC is found damaged upon power on. Only difference in our layout is that the isolated planes are 0.4mm apart. But I don't think this could be the cause of the problem. 

Could you please help me figure out why this IC is getting damaged?

  • 0
    TI__Mastermind 33115 points

    Nothing shown in the schematic/PCB would indicate a failure but I am recommending to follow the below comments in a future schematic/PCB revision.

    Schematic:

    1. R93=0Ω but this will short the isolation barrier?
    2. Remove R26
    3. Connect SYNC=SYNC_OK=GNDP
    4. Connect pins 6-8 to GNDP. These pins help with heatsinking and are not intended to be left floating
    5. Pins 9-12, 15-16 all connect to GNDS. Pins 10-12 help with heatsinking and are not intended to be left floating

    PCB:

    1. Isolated primary-to-secondary planes are close together and violate 8mm creepage/clearance required to realize full 5kV isolation rating.
    2. The distance between the pins shown below is concerning. Could it be that during assembly the IC may "float" in such as way that a short circuit is created between pins 1-2 or 2-3 or 3-4? I would recommend to not create copper pours that reduce the pin to pin pitch as shown below.

    Steve