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TPS1641: The device damaged during power up, and may shut off during operation

John11513
Expert 5540 points
Part Number: TPS1641

Hi Team,

Customer reported some issues with TPS16412:

1. Occasionally the device may be damaged during power up;

2. The device claimed features short circuit protection, while they found the device easily be destroyed when they did the output short circuit test. (output shorted to GND through a mechanical switch)

3. Occasionally the device may shut off during normal operation. The current limit threshold is about 1A, while the total system current is only 50mA/210mA (two different boards. both has such problem). Once shutting off, the device may resume work through cycling system power.

Here is the schematic: (sch shows 3 input source, actually there is only one accurate +24V input. They tested the power-up waveform, 24V_IN has about 3V overshoot during power up. say the highest input voltage is 27V.)

24V_IN Power-up waveform:

input current during power-up:

Could you please give me a hand about this issue?

Thank you!

John

  • 0
    TI__Guru 63015 points

    Hi John,

    I will get back before thursday EOD on this.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru 63015 points

    Hi John,

    1. During short circuit or supply generally we have seen that due to path inductance VIN can jump above device abs max and cause EOS damage.

    2. I will recommend to move TVS after the choke and choose lesser clamp voltage one to ensure it is clamped below VIN abs max of 42V. For robust clamping TVS should be close to VIN pin . Also if we increase caps close to VIN pin that will also absorb VIN spike.

    3. Regarding device turn off in steady state it could be FET IN-OUT short detection due to pulsating load. What is load profile?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Expert 5540 points

    Hi Kunal,

    Thank you for your advice. I think you are correct. I have asked customer testing your proposal.

    For point 3, yes the phenomenon seems like short detection. Do you mean the pulsating load result fault short detection? How should avoid fault trig? Customer think their load is stable, just several DC/DC, and the load of DC/DC is digital circuit working at constant clock frequency. How should they measure the load profile?

    Thank you!

    John

  • 0 in reply to John11513
    TI__Guru 63015 points

    Hi John,

    I will get back by tomorrow EOD on this.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    TI__Guru 63015 points

    Hi John,

    Customer can probe load current from input or output side of eFuse. If load current follows highlighted condition it can IN-OUT short detection:

    RRegards

    KKunal Goel

  • 0 in reply to Kunal Goel
    TI__Expert 5540 points

    Hi Kunal,

    What 'switching load' means? Is the switching mode DC/DC is switching load? Should customer measure the input ripple current and switching frequency. Considering table 8-3, if it means the high ripple current of down stream DC/DC will result fault trig of IN-OUT short detection?

    Thank you!

    John

  • 0 in reply to John11513
    TI__Guru 63015 points

    Hi John,

    Yes DC-DC is a switching load which draws current whose waveform looks like a sinusoid or a pulses. 

    Should customer measure the input ripple current and switching frequency. Yes

    Considering table 8-3, if it means the high ripple current of down stream DC/DC will result fault trig of IN-OUT short detection? Yes