consider we have a driver that drives a long signal & connects to an input device. At the input device there is either overshoot, undershoot or signal threshold violations, what are the various things that can be done to correct this problem
Usually the simplest thing to do is to add a series resistor at the output of the driver (at the beginning of the line). The sum of the driver's output resistance and the series resistor must match the line impedance.
well it seems using the resistors is the best solution.
but could any one explain to me how this solve the problem???
how did the addition of the resistor eleiminate the problem?
It works because usually the driver output impedance is lower than line impedance.
If the series resistor is not present the line is mismatched both at the drive end and at the load end. In such a situation you have reflections at both ends of the line and this results in overshoots and undershoots at both ends.
If the series resistor is close to the driver, the short trace between the driver and the resistor can be neglected and the driver has an output resistance equal to the line impedance. In this way the line is matched at the source but not at the load.
The effect of this is that you have only one reflection at the load end of the line.