Contents
How do you route a clock signal?
Lay out the fast clocks on the surface of the board, but keep them away from other traces (i.e. don’t route other traces in parallel with them, keep them separated from other traces by at least 3X the width of the clock trace to keep the mutual coupling below about 30db, make sure there’s an unbroken continuous return …
What is crucial for high speed design?
Power supply – power supply bypassing to minimize “noise” is especially important for high speed circuitry. Understanding the potential source of such inductance and avoiding this potential instability or resulting oscillations in the circuit is an important consideration for high-speed PCB design.
How fast is signal speed?
The speed of a “signal” or a pulse of electricity ,or light ,through either is about 200,000 km/hr.
What is the gap between two power planes?
Two gap lengths are chosen to compare a small vs large gap. It is not uncommon to have 50 mils separation between power planes, so that is what was used for worst case gap. A 5 mil gap is chosen for best case, which is a typical minimum for trace to pad clearance spec.
What happens when a signal crosses a split plane?
The takeaway message is that when signals cross a split plane, the transmitted signal sees an impedance mismatch causing a positive reflection for a time equal to the length of the gab, which increases the magnitude and shape of the FEXT pulse, thereby degrading the risetime of the transmitted signal proportional to the FEXT pulse shape.
What’s the best way to route a high speed signal?
Keep 135⁰ trace bends instead of 90⁰ while routing high-speed signals. The bends should be kept minimum while routing high-speed signals. If the bends are required, then 135° bends should be implemented instead of 90°as shown in figure (5, Right side).
What happens when microstrip signals cross the gap?
The first and last segments are 100 ohms differential and 56 ohms SE, while the trace impedances across the gap are ~134 ohms differential and ~103 ohms SE. Since the impedance across the gap is higher than the first and last segments, we expect to see be a positive reflection over the length of the gap.