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TPS566238: Damage of Device, will external output pin voltage be the reason?

Dave Chang
Expert 3325 points
Part Number: TPS566238

Hello SR support team,

We have experienced the device damage of TPS566238.

The happen rate would be 30%. (3 out of 10)

Please see the schematic here of TPS566238.

The issue happens that when output V3P3_STBY1 exists the voltage. 

After enable and Vin is provided, the V3P3_STBY1 will stop the PWM based on the theory, will this damage the device?

Here's the impedance of broken devices.

Thanks.

Best Regards,
Dave

  • 0
    TI__Mastermind 46810 points

    Hi Dave,

    What is purpose for D8 which is connected +V3P3_STBY to +V3P3_STBY1 (Output)? That means when you apply EN, then you add a voltage to output. It doesn't make any sense. TPS566238 is continuous current mode and could not support pre-bias output voltage. Please remove D8.

    Hope this helps,

    Thanks,

    Nancy

  • 0 in reply to Nancy Zhang
    TI__Expert 3325 points

    Hello Nancy,

    Thanks for your reply.

    The original design is for dual power (AUX power). When system is at S3 and S0, the power is possible to be delivered.

    However, the +V3P3_STBY is not able to output at S0, thus we need 12V to 3.3V rail.

    If the AUX is needed, can you suggest the suitable modification? Or any suggestion?

    Also, the IC failure may be related to the reason I listed above?

    Best Regards,
    Dave

  • 0 in reply to Dave Chang
    TI__Mastermind 46810 points

    Hi Dave,

    I am not an expert for your system S0/S3 and AUX power. Did you try to remove D8 and see if it works?

    Thanks,

    Nancy

  • 0 in reply to Nancy Zhang
    TI__Expert 3325 points

    Hello Nancy,

    Thanks.

    Our concern is when PWM circuit output side has the leakage voltage around 3.3 V, whether the PWM IC has the damaged risk or not before or during PWM IC boot up?

    From your response, we can’t figure out the answer. We can remove D8, but we still need to know the reason, thanks! 

    Best Regards,
    Dave

  • 0 in reply to Dave Chang
    TI__Mastermind 46810 points

    Hi Dave,

    1. I don't think the IC will damage with 3.3V pre-bias output voltage since the max output voltage for TPS566328 is 7V. Either before power up or during IC boot up.

    2. During power up, the internal amplifier compares the VFB and soft start voltage. If the VFB pin voltage is higher than the internal reference in soft start, the PWM won't start switching. That is the reason.

    3. Please try to remove D8 to see if is working and also see if IC was damaged.

    Thanks,

    Nancy