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SN65LVDS32: Failure effects for three different fault conditions

Colin Tombari
Prodigy 50 points

Part Number: SN65LVDS32

Tool/software:

Hello,

I am performing a Failure Modes Effects Analysis (FMEA), and the system uses the SN65LVDS32D and SN65LVDS31D driver and receiver pair. I would like to understand the effects of the following failures. Although I imagine they are extremely unlikely, the analysis dictates that I include all three.

1) If there is an input short to V-supply, does this result in the output stuck at a logic high? Or would there be no output? Would this failure be isolated to a single channel?

2) If there is an input short to GND, what would happen at the output? Logic low, high impedance, etc. Would this failure be isolated to a single channel?

3)  If there is a V-supply short through the device (high to low), what would be seen at the output? Would all channels be pulled low?

Thank you for your help,

Colin Tombari

Reliability Engineer

BAE Systems, Inc.

  • +1
    Guru 320720 points

    1./2. For the driver, voltages at VCC/GND are valid logic levels, and the outputs work normally. For the receiver, VCC/GND voltages will not damage the rest of the device, but when an input is VCC, the differential input signal might not be detected correctly; the output (if enabled) will drive low or high.

    3. If the supply voltage drops too much, the outputs will be inactive. But otherwise, it is unpredictable where exactly the short happens and what part of the device gets damaged, so it is unpredictable how the outputs behave.

  • +1
    TI__Genius 15321 points

    Hi Colin,

    Thanks for reaching out with your question on these devices.

    For the driver: As Clemens mentions, these are valid voltage ranges for a single-ended input. Would cause output to be stuck in high / low state.

    For the receiver: Short to Vsupply would cause the output to be stuck in a high state, as the supply voltage meets the datasheet specs of greater than 2V for VIH. (see section 8.3). To Clemen's point the differential may not be correctly detected if the short to Vcc was paired with another leg of the differential input that exceeds the values listed in Table 1 of the datasheet. Similarly, a short to ground would result in the output stuck in a logic low state for VIL, but also must meet the specs per Table 1. This device was not characterized under the third condition, and so it is not guaranteed as to how the output would behave. 

    Thanks, Amy

  • 0 in reply to Amy
    Prodigy 50 points

    Thank you!

  • 0 in reply to Colin Tombari
    TI__Genius 15321 points

    Please reach out for any other questions!

    -Amy