0
\$\begingroup\$

What are the consequences of a source terminator resistor (placed in series with the output) that is too high of a resistance value? Is it just a slower rise time at the input, or are there other consequences? Do I make ringing/reflections WORSE at the input if the source terminator is too high?

I am wondering what can go wrong if I just put a source terminator resistor in series with an output that makes the series resistance greater than the characteristic impedance of a short transmission line? (When I say transmission line, I'm talking about wire of a few inches, paired with a ground wire of same length.)

\$\endgroup\$
11
  • \$\begingroup\$ It sounds like you're asking about terminating a transmission line at first, but then talk about a GPIO pin. I can't make out what you're asking, and even what you think "terminating" actually means. \$\endgroup\$
    – Olin Lathrop
    Dec 13, 2016 at 19:27
  • \$\begingroup\$ I would not try to put 50uA through a transmission line. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Dec 13, 2016 at 19:28
  • \$\begingroup\$ @OlinLathrop - You're right, I will edit my question to get rid of the GPIO pin nonsense. My question should be simple: What happens when the source terminator resistor is too large of a resistance value? \$\endgroup\$
    – acker9
    Dec 13, 2016 at 19:30
  • \$\begingroup\$ See figures 3 and 4 of this application report. \$\endgroup\$
    – CL.
    Dec 13, 2016 at 20:34
  • \$\begingroup\$ Is the transmission line terminated in the characteristic impedance of the line? Most likely, if this is a digital signal only travelling a few inches, then it doesn't matter very much. You may not need the series termination at all. \$\endgroup\$
    – user57037
    Dec 14, 2016 at 2:49

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Browse other questions tagged or ask your own question.