pradeepbadrathwal
Newbie level 3
Hello,
I am doing simulation of an IO running at 200 Mhz. Load is given equal to 6pF with the following distribution :
- tx line of 3cm (PCB trace ) : so Tx load is 4.5pf ( 1.5pF per cm ).
- Z0 is 60 Ohms .
-1.5pF lumped at far end.
IO transition times are order of 2.5nS ( approximately equal to bit period ).
Two points i want to clear :
-How the 1.5pF per cm load would be calculated ? I have seen this figure is quoted by many standards, still do not clear how it is calculated ? and is this value frequency dependent? transition dependent ?
-I am doing simulation with tx + 1.5pF and without Tx with 6pF.
when i am connecting lossless tx line at io of 3cm with 1.5pF lumped capacitive load at far end, my transitions are relatively fast compared to the pure 6pF cpacitive load. It seems that transmission line is not showing equvilent cap of 4.5pF. Do i need to take extra cap at farend when doing simulation with tx line. Simulator is Eldo.
Kindly help.
Thanks ,
I am doing simulation of an IO running at 200 Mhz. Load is given equal to 6pF with the following distribution :
- tx line of 3cm (PCB trace ) : so Tx load is 4.5pf ( 1.5pF per cm ).
- Z0 is 60 Ohms .
-1.5pF lumped at far end.
IO transition times are order of 2.5nS ( approximately equal to bit period ).
Two points i want to clear :
-How the 1.5pF per cm load would be calculated ? I have seen this figure is quoted by many standards, still do not clear how it is calculated ? and is this value frequency dependent? transition dependent ?
-I am doing simulation with tx + 1.5pF and without Tx with 6pF.
when i am connecting lossless tx line at io of 3cm with 1.5pF lumped capacitive load at far end, my transitions are relatively fast compared to the pure 6pF cpacitive load. It seems that transmission line is not showing equvilent cap of 4.5pF. Do i need to take extra cap at farend when doing simulation with tx line. Simulator is Eldo.
Kindly help.
Thanks ,