LVDS is a bus where a current flows. So, if there is no terminator with a resistor, the right amount of current can’t flow. Hence, a terminator is mandatory.
The best thing is to connect one side of the cable with the source, e.g. the break-out board, and the other side with the terminator. In between, the DDS boards can be connected to the cable.
Building a terminator¶
First, one needs to order the PCB at a manufacturer. REMEMBER ONE NEEDS TWO TERMINATORS FOR ONE PULSE BOX! The required PCB file can be found in the folder \anna-c704calcium40ControlProgramsPBox documentslvds-terminator and is called lvds-terminator.PcbDoc. For each PCB, one needs two resistor arrays. The RS-Components order number can be found in the same folder in the file resistor_order.txt. Additionally, one needs a 50-pin-connector for each PCB, too.
When soldering the orientation of the resistors is not import, but the orientation of the 50-pin-connector is important!!! The first pin on the PCB (the only squared pin) has to be on the same side as the single slit (in the middle) of 50-pin-connector.