I am using two evaluation boards in my circuit. Counting the one I'm designing, there are three. I know the impedance of tracks on Board #1 and have control over the impedance of tracks on Board #2. The input impedance of the tracks on Board #3 is unknown. There is no termination at the end of the lines on Board #3.
At the interface between Board #2 and Board #3, I need to control the impedance. To that end, I will be source matching at the driver on Board #2, but what is the best way to deal with boundary?
Would it be best to have a termination at the end of the line on Board #2? Perhaps a shunt or AC Termination? This assumes my driver can support the power drain of the shunt.
Perhaps I should use a quarter wave transform? Ending the transform right at the input header to Board #3 might be effective?
The simplest solution might be to place the connector physically close to the driver so they are lumped. If I then add source termination resistors to the driver to match it to the impedance of Board #3, would the two boards communicate smoothly?
Since I don't know the impedance of Board #3, would it be reasonable to accurately measure the track's width and its distance from the ground plane and roughly calculate it?
Speed The edge rate of the data is ~750Mhz - 1GHz. I'm working with a rise time of about 1ns. I have space for a larger capacitive load if recommended. The output drivers of choice are the 74VCX245, but am open to changing them.
Board Layout Board #2 will have a solid ground plane between the output drivers and the connection to Board #3.
Connector Board #2 and Board #3 will connect via a 2x20 rectangular header. I am open to other suggestions.
Board #3 Board #3 is Texas Insrument's DAC7741 EVM. If you look at the data sheet, you'll see that there is not much information on the track design. The most I was able to extract was that the minimum track width is 10 mils, it is 1oz copper plated, and the layer (dielectric) thickness is approximately 0.014"