and the one referenced in the forum, a Panasonic ERJ2BQFR56X (0.56Ω), is a “Current Sensing Resistors Thick Film Type” of 0.166W (1/6W) which is… quite specialized and hard to find (it is only sold in a few places and the shipping cost here is hundreds of times higher than the cost of the resistor itself, you end up paying 1€ for a bunch of resistors and 12€ for the shipping 🤣).
So the questions are:
What are the ACTUAL specifications for the resistor?
Can’t it be 1/16W like the vast majority of 0420 resistors, instead of a 1/6W?
Why isn’t it 1k as shown in the diagram, but 0.56 instead?
Should have a 5% tolerance?
Panasonic ERJ2BQFR56X has 1%
And the most important one:
In which document can be found, P3768_A04_OrCAD_schematics(base_version).pdf aside?
This schematic version shows every component installed, hence the “base_version” in the file name, so it doesn’t match the stuffing on the actual shipping carrier board. Instead the better file to use in the carrier board reference files is P3768_A04_Concept_schematics.pdf, which shows the backup battery circuit as:
This reflects the actual component stuffing used on the board and matching P3768_A04_BOM.xls. J3, R560, and R222 are not stuffed, so those components would not be included in the BOM, as you found for R560. The 1k value does sound high - it would be better used if you need to measure the current on BBAT (with a 1% tolerance resistor). You could use 0 ohms or short across R560 instead. Do not install R222 and keep D4 since the pin is input only and cannot charge a battery or super capacitor.
I’ve checked those pdfs and those are basically the same file (same date, pcb rev, BOM rev), but showing you the gutted-off parts from dev kit carrier:
About literally bridging R560, good idea.
I was checking schematics of the old jetson nano b01 dev kit and that resistor doesn’t even exist, just the schottky diode to block reverse flow.
from the original jetson nano b01 dev kit carrier board pdf:
(same diode, no R560 between D4 and the connector)
// About R222, yep, I know that’s for jumping over the schottky diode and allow battery charging, thing that I’m not going to do (a typical CR2032 should last enough)
