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Overshoot and Undershoot at the input of 74HCT367

Hithesh
Genius 3290 points

We have an FPGA driving the hex buffer - 74HCT367. Because of the high rise times(400ps), there are big overshoots and undershoots at the input of the buffer.

How much of undershoot can the buffer tolerate? We are seeing upto -2v of undershoot at the buffer input.

The undershoot is for less than 5nsecs.

The device is supposed to have clamping diodes. I don't see the clamping happening. Is it because the edge rates are too fast for the diode.

 

 

  • TI__Expert 6330 points
    Hello,

    You want to make sure not to exceed the abs. max current for the part. In the abs. max section of the datasheet, the IK current is ±20mA. A series resistor can be used in order to limit the clamping current.

    Please note that we are trying to ensure that all posts are answered. With any new posts, we will be sure answer in a timely manner so that no posts go without a response. We will be closing this thread due to its age.
    Please feel free to post a new thread if you have additional questions, and we would be very happy to help.
    Best,
    Aaron Goodson