Pcie Design Guidelines; Table 7-9. Pcie Interface Signal Routing Requirements Up To Gen4 - Nvidia Jetson Orin NX Design Manual

7.2.1

PCIe Design Guidelines

The following table provides the PCIe routing guidelines for Gen3 and Gen4.
Table 7-9. PCIe Interface Signal Routing Requirements up to Gen4
Parameter
Specification
Data Rate / UI Period
Gen3
Gen4
Topology
Termination
Impedance
Trace Impedance
differential / Single Ended
Reference plane
Fiber-weave effect (Only required for Gen4)
Spacing
Trace Spacing (Stripline)
Pair – Pair
To plane and capacitor pad
To unrelated high-speed signals
Length/Skew
Breakout region (Max delay)
Gen 4.0 max trace:
Direct to device:
Insertion loss / length (delay)
Routing to 2 Orin Module
nd
Insertion loss / length (delay)
Routing to M.2 (NVMe) connector/card:
Insertion loss / length (delay)
Gen 3.0 max trace:
Direct to device:
Insertion loss / length (delay)
Routing to 2 Orin Module
nd
Insertion loss / length (delay)
Routing to PCIe/M.2 connector/module:
Insertion loss / length (delay)
PRELIMINARY INFORMATION
NVIDIA Jetson Orin NX
Requirement Units
8.0 / 125 Gbps / ps
16.0 / 62.5
Point-point
43
85 / 50
GND
•
Use spread-glass (denser weave)
instead of regular-glass (sparse
weave) to minimize intra-pair skew
•
Use zig-zag route instead of straight
to minimize skew, this is mandatory
for PCIe gen4 design
4x Dielectric
4x height
4x
41.9
-20.51 / 345 (2208)
dB / mm (ps)
-14.74 / 248 (1587)
-11.01 / 185 (1185)
-15.8 / 467 (2987) dB / mm (ps)
-10.5 / 310 (1985)
-7.6 / 224 (1437)
Notes
Unidirectional, differential. Driven by
100MHz common reference clock
Ω To GND Single Ended for P and N
±15%
Ω
Example of zig-zag routing (See Figure
7-11)
TX and RX should not be routed on the
same layer. If this is required in a design,
they should not be interleaved, and the
spacing between the closest RX and TX
lanes must be 9x Dielectric height
spacing.
ps Minimum width and spacing. 4x or wider
dielectric height spacing is preferred
Direct to device Insertion loss budget is
for PCB routing, connectors, and end
device (See Note 1). EM-370(Z) PCB
material is assumed in the length/delay
calculations:
Gen 4.0: -1.51 dB/in @ 8Ghz
Gen 3.0: -0.86 dB/in @ 4GHz
Length to delay calculations assumes 6.4
ps/mm (average of stripline and
microstrip).
The 2 Orin Module loss assumption is:
nd
Gen 4.0: -8 dB @ 8GHz
Gen 3.0: -6.5 dB @4GHz
The PCIe/M.2 connector/card loss
assumption is:
DG-10931-001_v0.1 | 32
USB and PCIe