The capacitive load of transmission

[chang830]

Hi

I am designing a block whcih will drive a transimission (50cm long) and a FPGA chip.The block will works in 1.25G.

I wonder, in simulation, how to define the load? especially the capacitive load? 5pF is enough?

BTW, the output of the block is PECL.

Thanks

 

[jallem]

You can model transmission lines in SPICE.
Although at the end the model is reduced
to a resistor(attenuation) in series, an
inductance in series(depending mainly of
distance) and a capacitor in parallel(depen
ding mainly from geometry).
The L/C combination is just a low pass
filter.