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TLV62568A: SW Output Failures

Jim G
Intellectual 706 points
Part Number: TLV62568A


We're currently experiencing a small level of fallout with devices using TLV62568ADRL as a 3.3V, 1.0A switching regulator.

The device input is 5V, fed from TI LM2678S-5.0.

Our schematic design based on the datasheet and Web Bench:

On failures we observe that the SW output of the device is shorted to ground.
Replacing the device resolves the issue.
We cannot find any issues farther downstream from devices powered by the 3.3V output.




I suspected possibly an overvoltage event at the Vin pin, but might expect that would damage both of the output devices instead of just the low side FET.
To explore this I tried to forward and reverse bias the body diodes in the output stage on 4 samples (2 good, 2 bad):


My measurements seem to suggest that the high side FET body diodes of the bad samples are intact (blocking reverse voltage), but their forward voltages certainly appear different.

Are there any other suggestions of what may be happening to these devices? ESD bogeyman is a possibility, but I'm trying to think of what else is possible to experimentally rule out.

  • 0
    TI__Mastermind 38541 points

    Hello Jim,

    Thanks approaching us for your queries.

    If my understanding is correct, LM2678S-5.0 supplies the TLV62568ADRL with 5.0V and only TLV failed in your board. To better understand the issue, please provide the following items below. 

    1. Is there any specs test conditions where TLV62568A were damaged on your board (ex. startup, power-down, steady-state, etc.)?

    2. Can you share schematic diagram which includes the circuit of the system load?

    3. PCB layout

    4. TLV62568A waveform (Vin, Vout, SW pin)

    If some of the items are confidential, you can share it via private message.

     

    Best regards,

    Excel

  • 0 in reply to Excel Regidor
    Intellectual 706 points

    Hi Excel,

    I will send you some additional information via private message. In short, the devices did function through our end-of-line ICT process when tested at the board level, passed testing, and then failed once installed in final devices. It's possible they are being damaged in our fixture, through ESD when handled, or by some anomaly in the end devices. However, once the damaged boards are replaced, the full device functions as expected.

    I'll send you some additional information privately,

    Jim

  • 0 in reply to Jim G
    TI__Mastermind 38541 points

    Hi Jim,

    I accepted your friend request so you can send a private message now.

    Best regards,

    Excel

  • 0 in reply to Excel Regidor
    TI__Mastermind 38541 points

    Hi Jim,

    As we are discussing this topic via private messaging, I will close this thread.

    Thank you.

    Best regards,

    Excel