Nvidia Jetson TX2 Manual page 27

USB 3.0 Design Guidelines
The follow ing requirements apply to the USB 3.0 PHY interfaces
Table 18. USB 3.0 Interface Signal Routing Requirements
Parameter
Specification
Data Rate / UI period
Max Number of Loads
Termination
Reference plane
Electrical Specification
Insertion Loss (IL)
Host
Device
TDR dip
Near-end Crosstalk (NEXT) @ DC to 5GHz
IL/NEXT Plot
Trace Impedance
Trace Impedance
Reference plane
Trace Length/Skew
Trace loss characteristic @ 2.5GHz
Breakout Region
Max PCB Trace Length
Max Within Pair (Intra-Pair) Skew
Differential pair uncoupled length
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 it is necessary to have interleaved routing in breakout, all the inter-pair spacing should follow the rule of inter-SNEXT
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
NEXT
(between TX/RX) Main-route
Min Inter-S
FEXT
(between TX/TX or RX/RX)
JETSON TX2/TX2i OEM PRODUCT | DESIGN GUIDE | 20180618
Requirement
5.0 / 200
1
90 differential
GND
Type C ≤ 2
Type A ≤ 7
Micro AB ≤ 1
Resonance Dip Frequency > 8
>= 75
<=-45
Diff pair / Single Ended 85-90 / 45-55
GND
< 0.7
Max trace length/delay 11 (73)
Host 152.3 (1014)
Device 50.8 (334)
0.15 (1)
6.29 (41.9)
Breakout 4.85x
3x
Breakout 1x
Main-route 1x
NVIDIA Jetson TX2/TX2i OEM Product Design Guide
Units Notes
Gbps / ps
load
Ω On-die termination at TX & RX
dB @ 2.5GHz
@ 2.5GHz
@ 2.5GHz
GHz The resonance dip could be caused by a via stub for
layer transition or trace stub for co-layout.
Ω Using TDR pulse with Tr (10%-90%) = 200ps
dB For each TX-RX NEXT
Ω ±15%
dB/in The following max length is derived based on this
characteristic. See Note 1.
mm (ps) Trace with minimum width and spacing
mm (ps)
Do trace length matching before hitting discontinuities
mm (ps)
mm (ps)
Dielectric
-
This is the recommended dimension for meeting
height
NEXT requirement
-
Intra-pair This is the recommended dimension for meeting
NEXT requirement
spacing
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