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Series resistors on high speed signal tracks
c64:
I have a TI chip which has output impedance 100Ω for pull-down and 150Ω for pull-up. But they still recommend adding 22Ω series resistors in datasheet. Why?
They don't specify output impedance but I calculated it from datasheet. If it says IOL is 4mA @ 400mV it means it's 100Ω right?
T3sl4co1l:
Yes, but is that worst case or best case?
Tim
c64:
Yes it's the worst case, you are right. So it's the maximum impedance. :-+
AndyC_772:
--- Quote from: c64 on July 16, 2020, 04:35:56 am ---I have a TI chip which has output impedance 100Ω for pull-down and 150Ω for pull-up. But they still recommend adding 22Ω series resistors in datasheet. Why?
--- End quote ---
Sometimes, engineers writing data sheets make mistakes, or offer advice that's not universally applicable. This is particularly true when it comes to layout guidelines.
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