Suppose I have a PCB that contains a microprocessor, or an FPGA (a "controller"). This "controller" drives a single-ended signal to an LVDS driver IC and a single-ended signal to a connector that goes out of the board. The output of the LVDS driver IC is then driven to the same connector that goes out of the board, as a differential pair.
If the board is specified as a board with controlled impedance, that is, 50ohms for single ended, and 100ohms for differential signals, does that specification only concern the signals going out of the board (single ended signal coming directly out of my controller and the output of the LVDS IC)? In other words, what significance does the characteristic impedance have for the signal that is not leaving my board (single ended signal going from the "controller" to the LVDS driver IC)?