Hi
I am doing a Spartan3 to Spartan 3 interconnect trough a ribbon (flat) cable with a characteristic impedance of 173R balanced (103R unbalanced). I have tried xilinx webcase to answer on the termination requirements of LVDS for spartan 3 withhout much luck. I got 2 different answers.
My questions are:
1) Can I use a ribbon cable with 173R balanced characteristic impedance? I have read that it should be 100R. The transmission is rather short, 300mm and relative slow in lvds terms. I would rather not switch the cable since it have other good properities that I rely on.2) With the above cable should the receiver end termination still be
100R3) With the above cable is a source resistor network necessary to match the impedance on the transmitter side and lower reflections? This is the point where xilinx tend to confuse itself in its datasheets for spartan 3. My dirty solution with adding 150R series resisor tend to give nicer signals.
Hope someone could help me on this.
Thanks in advance