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SN3257-Q1: S1B&S3B Short circuit to ground

Ethan Liu
Intellectual 865 points
Part Number: SN3257-Q1

Tool/software:

Hi team,

We use SN3257, and found in the experiment that the two pins S1B and S3B are short-circuited to the ground. My SA and SB are connected to two MCUs at the same time, and both MCUs fail at the same time. From the structure diagram, S1A and S1B should not be connected, so my other MCU will not be affected by the short circuit to the ground. However, this problem has occurred and we need a more detailed internal structure diagram.

1. Can you share internal structure diagram in detail?

2. Do you have any suggestiona about this issues?

BR,

Ethan

  • 0
    Guru 289110 points

    Apparently, the device got damaged. The most likely cause is overvoltage at these pins or D2. Are any of these pins connected to a cable/connector, or go through a noisy environment? Are these lines protected against overvoltage?

  • 0
    TI__Genius 10725 points

    Hello Ethan,

    Can you elaborate on the application? What are the input voltage and supply?

    This sounds like the device got damaged.

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    TI__Intellectual 865 points

    Hi Nir, Clemens

    The power input of the product is 14V, and the converted power input to SN3257 is 3.3V. These pins are connected to the MCU, and some of them need to be transmitted to the second MCU through the connector. It is damaged during the high and low temperature experiment. I judge that it is not a noisy environment, and the load is very low and it is not a harsh working condition. Our pin-cut power supply has over-voltage and under-voltage diagnosis, and if the power supply part is over-voltage, it will be protected.

    Can you share internal structure diagram in detail?

    BR,

    Ethan

  • 0 in reply to Ethan Liu
    Guru 289110 points

    If there is a connector, the I'd guess that the overvoltage comes from ESD or arcing. Are there any protection components on these lines?

  • 0 in reply to Ethan Liu
    TI__Genius 10725 points

    Hello Ethan,

    We cannot share internal structure information.

    Did this issue occur on one device? Have you tried testing other devices to see if they fail as well?

    Thanks,

    Nir 

  • 0 in reply to Nir Gilgur
    TI__Intellectual 865 points

    Hi Nir,

    We have verified it by ABA swap, and this fault follow by the issued device, and we have found 6pcs now.

    We are directly connected to one MCU through a connector, and the other MCU is directly connected to the MCU without any protection components. The one with the suffix M is directly connected to the MCU, and the one with the suffix FM is connected to another MCU through a connector. The damaged ones are PIN3 and PIN6, which are the signals transmitted to another MCU through the connector.

    BR,

    Ethan

  • 0 in reply to Ethan Liu
    Guru 289110 points

    If it is allowed likely possible that any of these lines can be touched, or that the boards are (un)plugged while powered, then that is the likely cause.

    Clamping diodes to VCC/GND would help, alternatively TVS/ESD diodes. (Place these near the connector.) For many kinds of signals, it is possible to add a series resistor (between the diodes and the device) for even more protection.

  • 0 in reply to Ethan Liu
    TI__Genius 10725 points

    Hello Ethan,

    The SN3257-Q1 has powered off protection up to 3.6V. I am not sure if this is an overvoltage event when the device is powered on or off. 

    What are the voltage signals passing through the mux? Is it possible to measure the voltage and current when the issue occurs? 

    I agree with Clemens suggestion of adding protection on the signal lines. 

    Thanks,

    Nir