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DS91M040: Vcc shorting to GND in driver mode

Matthew Palmore
Prodigy 10 points
Part Number: DS91M040

Tool/software:

We’re currently trying to debug an issue with DS91M040 (transmit mode only) and DS91M040TSQE/NOPB (receive mode only). I was wondering in which conditions would you end up blowing out the output of DS91M040? Would having the DS91M040 on and enabled going to the DS91M040TSQE/NOPB when it is powered of (so possible unknown state)? Are there any other situations that may cause Vcc to get shorted to ground when powering up or during operation? 

  • 0
    Prodigy 10 points

    Also what would happen if the Transmitter (on state) has only one output that goes to 2 differential inputs of the receiver (off state)? And there's a termination resistor on the transmitter side and not receiver side? Also what would happen if that termination resistor is 3k and not 100 ohms like it should be?

  • 0 in reply to Matthew Palmore
    TI__Genius 15321 points

    Hi Matthew,

    Thank you for your question.

    In the datasheet, DS91M040 125 MHz Quad M-LVDS Transceiver datasheet (Rev. M) the "Absolute Maximum" (page 4) conditions allow for a "continuous" output short circuit current. However, it is not recommended to run under Abs/Max conditions for extended periods of time. Page 5 of the datasheet lists the Differential short-circuit output current recommendations for the driver and receiver. Figure 6 shows the test setup under which these conditions were characterized. The transmitter side is a differential output (page 2). For an example of recommended device implementation, please refer to the evaluation module DS91M040EVK Evaluation board | TI.com and user's guide 125 MHz Quad M-LVDS Transceiver Evaluation Board. The termination must be matched so that there is not significant ringing / signal reflections on the bus.

    Thank you, Amy

  • 0 in reply to Amy
    Prodigy 10 points

    Hi Amy, we are trying to understand why this can occur. Can you tell us what is underneath in the IC specifically where the problematic burns on the IC are? Regarding other questions, is it possible for the for this (or another that this is connected to) IC to latch up if it is powered on when connected to another transceiver that is the same part?  

  • 0 in reply to Matthew Palmore
    TI__Genius 15321 points

    Hi Matthew,

    Do you have a schematic that I could review? If you would prefer to move this over email, that is another option if you are unable to share here.

    Does the device function?

    Thank you, Amy

  • 0 in reply to Amy
    Prodigy 10 points

    Yes, I think email would be easier. So I'm not allowed to send out the schematic but I think I'm allowed to draw up a mock schematic that explains the current setup. The device isn't operational, VCC is shorted to GND

  • 0 in reply to Matthew Palmore
    TI__Genius 15321 points

    Hi Matthew, 

    Abs/ max conditions allow for "continuous" output short circuit current. However, it is not recommended to run under Abs/Max conditions for extended periods of time. Have you tried swapping the part? Have you isolated anything else in the setup that could have led to the short?

    Thank you, Amy