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3.2
USB SuperSpeed Hub
The USB SS hub design uses a Realtek RTS5420 device. The hub circuit includes an SPI FLASH
device which holds configuration information. A design intending to duplicate the developer kit
hub implementation should include the same SPI FLASH programmed to match, or the hub
should be customized with fuses with the same settings. The configuration in the SPI FLASH
includes the following:
Power enables (DPS1/2/3/4_PWR) set to be active high
Charging feature disabled
SSC valid
3.3
Power over Ethernet
The P3509 carrier board includes a 4-pin Power over Ethernet (PoE) header (J19) which brings
out the VC power pins of the Ethernet connector. To use this alternate PoE power mechanism
to power a custom carrier board, the design would require a power converter to take the high
voltage PoE supply (38V-60V) and convert it to the correct voltage for the custom carrier board.
3.4
TI TXB0108 Level Shifters
The P3509 carrier board uses these level shifters to shift many of the signals going to the 40-
pin header from 1.8V to 3.3V. The design of these level shifters supports bidirectional signaling
without the use of a direction signal but has some side effects that should be considered. See
Jetson Nano Developer Kit 40-Pin Expansion Header GPIO Usage Considerations
the
Application Note
for details.
3.5
Features Not to be Implemented
The Jetson Xavier NX Developer Kit carrier board has some features that should not be copied
as they are not required or useful for a custom carrier board design. The ID EEPROM (P3509 -
U17) is a feature that is used for NVIDIA internal purposes, but not useful on a custom design.
A similar function may be desired for a custom design, but the NVIDIA software will not
interact with these devices and the I2C address used by the developer kit carrier board ID
EEPROM on the I2C2 interface (7'h57) should be avoided.
NVIDIA Jetson TX2 NX
Developer Kit Feature Considerations
DG-10141-001_v1.1 | 8
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