Nvidia Jetson Orin NX Design Manual page 33

Parameter
Near End Crosstalk (NEXT)
Impedance
Trace Impedance: Diff pair / Single Ended
Reference plane
Trace Length/Skew
Trace loss characteristic:
Gen1
Gen2
Breakout Region – Max length
Max Trace Length (delay)
Gen1 Host
Gen1 Device
Gen2 Host or 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
PRELIMINARY INFORMATION
NVIDIA Jetson Orin NX
Requirement Units
≤ −45 dB
85 / 43 Ω
GND
< 0.6 dB/in @ 2.5
< 1 GHz
dB/in @ 5G Hz
11 mm
160 (1071) mm (ps)
107 (714)
114 (765)
0.15 (1) mm (ps)
6.29 (41.9) mm (ps)
4x / 3x Dielectric
4x / 3x height
4x / 3x
4.85x Dielectric
3x height
11 mm
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 if total channel loss meets IL spec
0.4 mm
USB and PCIe
Notes
DC – 5GHz per each TX-RX NEXT
±15%. Intrinsic Zdf, does not account
for coupling from other trace pairs
Based on the dielectric material
EM370(Z). The following max length is
derived based on this characteristic.
The length constraint must be re-
defined if the loss characteristic is
changed.
Note that microstrip loss could be
similar to stripline due to humidity
effect.
Minimum trace width and spacing
Stripline (6.7ps/mm) assumed.
CMC use length reduction = 30 mm
(Gen1/2).
ESD use length reduction = 10 mm
(Gen1), 12.5 mm (Gen2).
Do not perform length matching within
breakout region. Trace length matching
should be done before discontinuities.
(between TX/RX pair
NEXT
This is the recommended dimensions
for meeting the NEXT requirement.
Stripline structure in a GSSG structure
is assumed (holds in broadside-coupled
stripline structure)
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 7-5.
GND via is used to maintain return
path, while its Xtalk suppression is
limited
long via stub requires review (IL and
resonance dip check)
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