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AM26C31: Undershoot

Shinu.V.Mathew
Genius 10530 points
Part Number: AM26C31

Hi Team,

Customer is using AM26C31 differential line driver in one of the project for LCD interface and observed that input signal to line driver has some negative undershoot around -0.5 to -0.7V present on ~12-20ns time stamp for all inputs continuously (attached image). Lines are direct interfaced from FPGA to AM26C31 without any termination on board. All LCD burst pulses are transmitted continuously every 10ms as per our application .

Initially customer tested with off the shelf LCD box which doesn’t have proper termination and observed -0.7V undershoot. Then terminated one of the differential signal with 100R resistor for testing purpose and observed the input pulse at pin 1 but still the negative undershoot is present at the input. However, negative undershoot level decreases subsequently at differential output around -0.2-0.3V.

 

As per datasheet it showing min input voltage -0.5V.

 

Customer would like to the whether this IC will damage over the time and/or may face some reliability issue.

Regards, Shinu Mathew. 

  • 0
    TI__Mastermind 26806 points

    Shinu Mathew,

    Your images are not showing up on my end, so I want to make sure my understanding is correct: You're saying that the customer's application is experiencing -0.7 V undershoot at the A pins (i.e. pins 1A, 2A, 3A, and/or 4A)?

    Exceeding the Absolute Maximum Ratings of the device can certainly cause issues. Allowing the device to be exposed to this undervoltage condition routinely, continuously, and/or over a period of time as you described would affect the reliability of the device.

    I'd recommend - if possible - adding either a limiting resistor or other termination that would keep the signal within spec. Would this be possible for the customer?

    Best,

    Danny