Nvidia Jetson Xavier NX Design Manual page 33

Parameter
GEN1
GEN2
Near End Crosstalk (NEXT)
Impedance
Trace Impedance: Diff pair / Single Ended
Reference plane
Trace Length/Skew
Trace loss characteristic (max):
GEN1
GEN2
Breakout Region – Max length
Max Trace Length
GEN1 (Host)
GEN2 (Host/Device)
Max Trace Length (Device)
Max Intra-Pair Skew (RX/TX_N to RX/TX_P)
Differential pair uncoupled length
Trace Spacing for TX/RX Interleaving
Trace Spacing: Microstrip / Stripline
Pair-Pair
To Ref plane and SMT pad
To unrelated high-speed signals
Trace Spacing for TX/RX Non-interleaving
TX-RX Xtalk is very critical in PCB trace routing. The ideal solution is to route TX and RX on different layers.
If routing on the same layer, strongly recommend not interleaving TX and RX lanes
If have to have interleaving routing in breakout, all the inter-pair spacing should follow the rule of inter-S
spacing)
The breakout trace width is suggested to be the minimum to increase inter-pair spacing
Do not perform serpentine routing for intra-pair skew compensation in the breakout region
Min Inter-S (between TX/RX)
NEXT
Breakout
Main-route
Max length
Breakout
Main-route
Via
Topology
GND via
Max # of Vias
PTH vias
Micro Vias
Max Via Stub Length
Additional Component Placement Order
NVIDIA Jetson Xavier NX
Requirement
75
75
≤ −45
85 / 43
GND
0.7
0.9
11
152 (1014)
127 (850)
GEN1 only 51 (334)
0.15 (1)
6.29 (41.9)
4x / 3x
4x / 3x
4x / 3x
4.85x
3x
11
Max trace length -
L
BRK
Y-pattern is recommended
Keep symmetry
Place GND via as symmetrically as
possible to data pair vias. Up to 4
signal vias (2 diff pairs) can share a
single GND return via
4 if all vias are PTH via
Not limited as long as total channel loss meets IL spec
0.4
Chip ̶ AC capacitor (TX only) ̶ common mode choke ̶ ESD ̶ Connector
Units Notes
Ω @ Tr = 200ps (10%-90%)
@ Tr = 61ps (10%-90%)
dB DC – 5GHz per each TX-RX NEXT. See
(See Figure 6-3) and Figure 6-4)
Ω ±15%. Intrinsic Zdf, does not account
for coupling from other trace pairs
The following max length is derived
dB/in @ 2.5GHz based on this characteristic. The length
dB/in @ 5GHz constraint must be re-defined if loss
characteristic is changed. The trace
loss profile for Gen2 support is based
on the dielectric material EM370(5).
mm Minimum trace width and spacing
mm (ps)
mm (ps)
mm (ps) Do not perform length matching within
breakout region. Trace length matching
should be done before discontinuities.
mm (ps)
Dielectric
height
This is the recommended dimensions
Dielectric for meeting the NEXT requirement.
height Stripline structure in a GSSG structure
is assumed (holds in broadside-coupled
stripline structure)
mm
Y-pattern helps with Xtalk suppression.
It can also reduce the limit of the pair-
pair distance. Review needed
(NEXT/FEXT check) if via placement
does not use Y-pattern. See Figure 6-5.
GND via is used to maintain return
path, while its Xtalk suppression is
limited
mm long via stub requires review (IL and
resonance dip check)
DG-09693-001_v1.7 | 22
USB and PCIe
(between TX/RX pair
NEXT