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Broken SN65LVDS1 IC

Jonathan Lee4
Prodigy 50 points
Other Parts Discussed in Thread: SN65LVDS1, SN65LVDT2

Recently a customer returned a unit where 2 SN65LVDS1 were no longer driving signals. Outputs Z and Y were both at ground level. Is this failure due to a voltage or current overload? Measuring resistance with a multimeter from ground to the outputs pins measured around 12-15 Ohms.

The board that the chips were on is part of a central board that uses the SN65LVDS1 to communicate with SN65LVDT2 chips on satellite boards.  The satellite boards are between 6 to 30 feet away. In this case, 2 of 3 SN65LVDS1 chips to a particular satellite board were no longer working. All other SN65LVDS1 chips are working. The SN65LVDT2 chips on the particular satellite board are still working.

  • 0
    TI__Prodigy 420 points

    Hi, Jonathan,

    The output Z and Y are always at different levels(0 or 1) when normal work.  And the resistance between the pin and ground is typically several Mega ohm when float. So it's really strange as your description.

    You can compare  the consuming current of this abnormal board with one normal board. It might be different if the ic is broken by some reason.You also can try to replace it with a new ic to check whether it works well.(don't abandon the replaced ic).

    Eric 

  • 0 in reply to Eric Xiong
    Prodigy 50 points

    Hi Eric,

    The parts were replaced and the communication is working again, leading me to believe ic was broken.

    Jonathan

  • 0
    TI__Prodigy 420 points

    Hi, Jonathan,

    So output protect diode may be broken by overload current or voltage. And how may unit have this same problems? Did you know whether this customer operate the ic beyond absolute maximum ratings?

    Eric

  • 0 in reply to Eric Xiong
    Prodigy 50 points

    Hi Eric,

    Each board has 12 of these chips. So far, we have delivered 10 boards. This is the first board to have the issue. On that board, 2 chips broke. The board is designed to take 28V and generate 3.3V through a switching regulator. The drivers on the main board and the receivers on the satellite boards are powered through the same 3.3V.

    I don't believe the chips saw an overvoltage as all chips are on the same powerform and only 2 broke. The only thing the customer could have done was to hotplug the particular satellite board as the satellite board is in another enclosure. The units were designed so the main board and satellite boards would power up together.

    The customer was working in a lab environment so temperature and humidity should not be an issue. The boards are also enclosed in a metal enclosure.

    Jonathan

  • 0 in reply to Jonathan Lee4
    Prodigy 50 points

    Hi Eric,

    Is there anything in particular I can look at on the broken IC to see if it was an overvoltage or overcurrent failure?

    Jonathan

  • 0 in reply to Jonathan Lee4
    TI__Prodigy 420 points

    Hi, Jonathan,

    I think there is little way to judge the damage reason by broken IC. But we can do the failure analyze to check which part inside is broken if there are many failure IC emerge in your product. 

    Eric