Hello,
I have a design that has a modular expansion system where each expansion slot has a 25MHz clock running LVDS out of the LMK00301.
Because of the nature of the design, each of these slots may or may not have a card loaded, and thus not have a termination. In our prototype phase, we determined that placing the termination resistor on the main board rather than close to the receiver resulted in undesirable signal integrity, so now we are faced with a few choices.
We can either keep the termination resistor on the main board and ensure that the LVDS signal is always terminated, but the received signal integrity is degraded, OR we can move the termination resistor close to the receiver and onto the expansion card, fixing signal integrity for loaded cards, but resulting in unterminated LVDS lines on the main board.
My questions are this:
- What sort of problems/degradations would we see by failing to terminate unused outputs of the LMK00301?
- Is there an alternate termination scheme that would make for improved signal integrity and prevent the problems caused by unterminated outputs?
Thanks,
Jeff
