I am working on designing my first high-speed PCB with 4 layers (in order):
- Top Layer: Single-ended/TTL signals
- Internal Layer 1: Power Plane (3.3V)
- Internal Layer 2: Ground Plane
- Bottom Layer: LVDS signals
I have some critical connections made on the top layer but due to the layout of the PCB (which is pretty much fixed due to mechanical restrictions) I am unable to fit all of the single-ended signal traces on the top layer. Would there be a downside to moving some of these onto the second layer (containing the power plane), or should I leave the plane unbroken? The internal planes are intended to isolate the single-ended signals from the differential traces, and considering the ground plane (the plane closest to the LVDS traces) is still unbroken I was wondering if this could be done without causing signal integrity issues.