Aurora Interface Board Layout Guidelines
Aurora interface runs at speeds up to 5Gbps, which means high-speed board layout
guidelines and practice must be considered while routing Aurora physical interface from
the transmitter to the receiver.
On the iC6000 side the Aurora interface lines are connected directly to the FPGA implementing
the physical Aurora interface. These lines exhibit the following characteristics:
Aurora receive data lanes (AGBT_TX marked on the target side)
To ensure interoperability between drivers and receivers of different vendors, AC coupling at
the receiver input is used. 100nF AC coupling capacitors for connection to the transmitter are
used at Aurora receiver input pins.
Aurora transmit data lanes (AGBT_RX marked on the target side)
This direction is normally not applicable for Nexus trace operation. The iC6000 has no AC
coupling capacitors on these lines. They must be located on the target (receiver) side.
Aurora clock lane (AGBT_CLK marked on the target side)
100nF AC coupling capacitors are located on the CLK output to protect drivers from possibly
getting shorted. Target side has usually its own AC coupling.
The following guidelines should be considered during the target board layout design to ensure
the correct operation of the Aurora trace interface. Note that the quality (signal integrity) of the
Aurora interface signals to the external Aurora capable trace tool is critical for correct and
reliable trace operation.
·
All Aurora trace port lines on the PCB should be as short as possible (max 2.5 cm).
·
Traces should run on the same layer, or layers with the same impedance.
·
Preferred layer impedance is 50 Ohm.
·
Samtec ERF8 connector ground pins should be connected directly to the PCB GND plane.
·
Trace clock should have only point-to-point connection. Stubs must be strictly avoided.
·
It is strongly recommended for the data lines to be point-to-point only too. If any stubs are
needed, they should be as short as possible. When longer are required, there should be a
possibility to optionally disconnect them (e.g. by solder jumpers).
Trace port data bus inner crosstalk is not so important, but it is critical to isolate the whole bus
from the other target signals, including from the Aurora trace clock.
