Nvidia JETSON TX2 - General Routing Guidelines

NVIDIA Jetson TX2/TX2i OEM Product Design Guide
JETSON TX2/TX2i OEM PRODUCT | DESIGN GUIDE | 20180618 21
4.0 GENERAL ROUTING GUIDELINES
Signal Name Conventions
The follow ing conventions are used in describing the signals for Jetson TX2/TX2i:
▪ Signal names use a mnemonic to represent the function of the signal. For example, Secure Digital Interface #3
Command signal is represented as SDCARD_CMD, w ritten in bold to distinguish it from other text. All active low
signals are identified by a # or an underscore follow ed by capital N (_N) after the signal name. For example,
RESET_IN# indicates an active low signal. Active high signals do not have the underscore-N (_N) after the signal
names. For example, SDCARD_CMD indicates an active high signal. Differential signals are identified as a pair
w ith the same names that end w ith _P & _N, just P & N or + & - (for positive and negative, respectively). For
example, USB1_DP and USB1_DN indicate a differential signal pair.
▪ I/O Type The signal I/O type is represented as a code to indicate the operational characteristics of the signal. The
table below lists the I/O codes used in the signal description tables.
Table 12. Signal Type Codes
Code
Definition
A
Analog
DIFF I/O
Bidirectional Differential Input/Output
DIFF IN
Differential Input
DIFF OUT
Differential Output
I/O
Bidirectional Input/Output
I
Input
O
Output
OD
Open Drain Output
I/OD
Bidirectional Input / Open Drain Output
P
Power
Routing Guideline Format
The routing guidelines have the follow ing format to specify how a signal should be routed.
▪ Breakout traces are traces routed from a BGA or other pin array, either to a point beyond the array, or to another
layer w here full normal spacing guidelines can be met. Breakout trace delay limited to 500 mils unless otherw ise
specified.
▪ After breakout, signal should be routed according to specified impedance for differential, single-ended, or both (for
example: HDMI). Trace spacing to other signals also specified.
▪ Follow max & min trace delays w here specified. Trace delays are typically show n in mm or in terms of signal delay
in pico-seconds (ps) or both.
- For differential signals, trace spacing to other signals must be larger of specified × dielectric height or inter-
pair spacing
- Spacing to other signals/pairs cannot be smaller than spacing betw een complementary signals (intra-pair).
- Total trace delay depends on signal velocity w hich is different betw een outer (microstrip) & inner (stripline)
layers of a PCB.