Startup Input Buffering

,

I am designing a custom carrier board. In 2.5.1 of the Nano datasheet, it says the following:

I/O pins cannot be high (>0.5V) before SYS_RESET* goes high. When SYS_RESET* is low, the
maximum voltage applied to any I/O pin is 0.5V. For more information, refer to the Jetson Nano
Product Design Guide.

First off, I cannot find any relevant information in the PDG as the note suggests. Any idea where it is?

Second, I plan on using a buffer for inputs until the system is booted. What all pins need to be buffered? ethernet lines (to Nano)? UART? SPI? I2C?
(nano will be the master device)
I plan to have HDMI_HPD and SYS_EN buffered as well.

I also might have to add HDMI input to the nano. I understand that I need an external device to enable the Nano to receive HDMI input. However, once I decide on how to tackle that, is that essentially another 10+ pins that I will need to buffer?

Thanks

Hi, please just follow the Design Guide to make custom design and the key point is to follow the power sequence as listed in DG.

I didn’t see anything referring to I/O pins during the power up sequence in the DG. I assume you are talking about “Carrier Board Supplies.” If so, that makes sense for most of our I/O, but we have some connections that go directly to the Nano, not depending on any logic/ICs on the board. Therefore, these components can be transmitting to the Nano before SYS_RESET* is high. These include a USB connection, ethernet lines, and HDMI*. I assume these will have to be buffered.

*(I assume only HDMI_HPD is relevant here, because this pin specifically can be driven high by the display device)

I may also have HDMI input to the Nano. I am not sure what the solution will be, but it may be through PCIE. If that is powered via the same 5V rail that the Nano is, I will have to buffer it I assume.

Any comments on these assumptions? Do I need to buffer all these pins?
Thanks

Generally no buffer is necessary on USB, ethernet and HDMI, you can check the P3449 schematic in DLC for reference.

great, thanks

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.