• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 20 subscribers
  • Views 531 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

txs0108e: TXS0108e overshoot

Jon Bean1
Expert 1130 points
Part Number: TXS0108E

Hi

I am using the TXS0108E to interface a 1MHz clock from 3.3V to 5V. I am finding that I am getting a lot or over/under shoot on the clock edges. I have manged to clean this up on the 3.3V side by using an ac termination of 50R and 470n. But if i do the same on the 5V side it makes the signal no better. I still have some overshoot but the signal amplitude is reduced and I get a rising edge slope. Does anyone have any thoughts on how to clean up the signal?

Thanks

  • 0
    TI__Guru* 97046 points
    Overshoot is extremely common in logic circuits due to low impedance outputs driving high impedance inputs (basically the definition of a CMOS logic circuit). Is the overshoot causing damage or problems with the system?

    I would recommend adding a series resistor to the line to protect the 5V device if the overshoot is a problem. The only other option I know of is to add clamp diodes to the line to cut off any excessive voltage.
  • 0 in reply to Emrys Maier
    Expert 1130 points

    The issue is that the signal is feeding the clock input of a image sensor. The clock overshoot is causing noise on the sensor output. Only a few mV but I am trying to measure values down to a few 100uV so its not great. I just dont understand how nothing that I do make a difference, I have a clean signal going in but the output has the overshoot.

  • 0 in reply to Jon Bean1
    TI__Guru* 97046 points
    You could try loading adding a capacitive load to the output to slow it down - essentially (very oversimplified) the fast output edges cause overshoot. Maybe 30-50pF?