Nvidia Jetson AGX Xavier Series

USB, PCIe, and UFS
Jetson AGX Xavier Series Product DG-09840-001_v2.5 | 50
7.2.1 PCIe Design Guidelines up to Gen3
The following table details the PCIe design guidelines up to Gen3. See Section 7.2.2 for design
guidelines regarding PCIe Gen4.
Table 7-12. PCIe Interface Signal Routing Requirements up to Gen3
Parameter
Requirement
Units
Notes
Specification
Data Rate / UI Period
5.0 / 200
Gbps / ps
2.5GHz, half-rate architecture
Configuration / Device Organization
1
Load
Topology
Point-point
Unidirectional,
differential
Termination
50
Ω
To GND Single Ended for P and N
Impedance
Trace Impedance differential / Single Ended
85 / 50
Ω
±15%. See note 1
Reference plane
GND
Spacing
Trace Spacing (Stripline/Microstrip)
Pair – Pair
To plane and capacitor pad
To unrelated high-speed signals
3x / 4x
3x / 4x
3x / 4x
Dielectric
TX and RX should not be routed on the
same layer. See Note 2.
Length/Skew
Breakout region (Max Length)
41.9
ps
Minimum width and spacing. 4x or
wider dielectric height spacing is
preferred
Trace loss budget (for carrier board routing)
Routing direct to device
Routing to PCIe/M.2 connector
-14.5
-10.5
dB/in
@ 4GHz (See TBD),
Loss: GEN3 budget – module – end
device (-22dB + 3.5.dB + 4dB)
Loss: GEN3 budget – module – end
device (-28dB + 4.24dB + 8dB)
Max trace length (delay)
Direct to device on carrier board
Stripline
Microstrip
Routed to PCIe or M.2 connector
Stripline
Microstrip
491 (3383)
460 (27.19)
355 (2450)
333 (1969)
in (ps)
Mid-loss PCB of 0.8dB/in (Microstrip) or
0.75dB/in (Stripline) is used. Also,
6.9ps/mm for Stripline routing and
5.9ps/mm for Microstrip.
Max PCB via distance from the BGA
41.9
ps
Max distance from BGA ball to first PCB
via.
PCB within pair (intra-pair) skew
0.075 (0.5)
mm (ps)
Do trace length matching before hitting
discontinuities
Within pair (intra-pair) matching between
subsequent discontinuities
0.075 (0.5)
mm (ps)
Differential pair uncoupled length
41.9
ps
Via
Via placement
Place GND vias as symmetrically as possible to data pair vias. GND via
distance should be placed less than 1x the diff pair via pitch
Max # of Vias
PTH Vias
Micro-Vias
2 for TX traces and 2 for RX trace
No requirement
Max Via stub length
0.4
mm
Longer via stubs would require review
Routing signals over antipads
Not allowed