willycat
Newbie level 6
Hi,
to reduce reflection and crosstalk, i want to place a serial resistor as close to the output pin of a PIC18F4550 used as a clock signal. But how to determine the output impedance of that pin ?
Is it 0.7/3e-3 = 233 ohms (According to datasheet on page 380, with IOH=-3mA and VOH = VDD-0.7) ?
or 10e-9/50e-12 = 200 ohms (According to datasheet on page 389, TioR = TioF = 10ns when the load is 50 pF) ?
In both cases, i think it is too big, so i am probably wrong.
What is the correct value ?
Thanks,
willy.
to reduce reflection and crosstalk, i want to place a serial resistor as close to the output pin of a PIC18F4550 used as a clock signal. But how to determine the output impedance of that pin ?
Is it 0.7/3e-3 = 233 ohms (According to datasheet on page 380, with IOH=-3mA and VOH = VDD-0.7) ?
or 10e-9/50e-12 = 200 ohms (According to datasheet on page 389, TioR = TioF = 10ns when the load is 50 pF) ?
In both cases, i think it is too big, so i am probably wrong.
What is the correct value ?
Thanks,
willy.