Series Termination
- From: heilig.brian@xxxxxxxxx
- Date: Sat, 21 Feb 2009 09:48:11 -0800 (PST)
I am trying to understand series termination for a board I'm designing
with a Cyclone II FPGA. The Cyclone II has internal series termination
resistors making it easier for me. These resistors are typical 50 ohms
(25 in some cases). I assume the traces on my board must also be a 50
ohm transmission line so I plug some numbers into a microstrip trace
impedance calculator (at http://www.chemandy.com/calculators/microstrip-transmission-line-calculator-hartley27.htm
using specs for the board from http://www.expresspcb.com/ExpressPCBHtm/SpecsStandard.htm)
and it says I need a trace that is 1.5 mm wide. That trace is too
wide...it'll cover three pins! I think I must be missing something
because when I look at a PCB I don't see traces this wide for data.
Thanks for your help,
Brian
.
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