I am working on a new custom PCB to connect to the B404X with some custom sensors. Previously, we had used a Boron Board to interface with our sensors, but while building in the power delivery architecture, I noticed that the Torex 3.3V Buck Converter (XC9258B33CER-G) is EOL, and there are some discrepancies between the SoM Evaluation Board and Boron Board. Both the designs use this part, though the inductor/capacitor sizing differs between the two.
I was wondering if your team is planning to integrate a new part that we might leverage, as well, to keep the design as consistent as possible? If not, any recommendations or pitfalls to avoid would be great to know, as I am always hesitant to swap out a part known to work. Also, I was wondering what the motivation was on the Evaluation Board for utilizing a 2.2uH inductor, which differs from the 4.7uH, recommended by Torex and used in the Boron design?
The 1A max current output and ripple seems sufficient for our application and works well with our connecting sensors for our Boron-based PCB.
I don’t know why the 2.2 uH part is used, but I double-checked the BoM and it’s definitely 2.2uH.
L7
FIXED IND 2.2UH 4A 61 MOHM SMD
Bourns,Inc. SRP4020TA-2R2M
The Photon 2 has a MPS MP1601GTF-Z, however I would probably use whatever you can get and follow the datasheet instructions.
These are the requirements for your 3V3 regulator:
3V3 is used to supply power to nRF52840, logic ICs, memory, etc… The 3V3 input voltage range is between 3V to 3.6V DC, but 3.3V is recommended. Make sure that the supply can handle a minimum of 150 mA, however we recommend a minimum of 500 mA supplied from your base board to allow for compatibility with future modules.
These limits do not include any 3.3V peripherals on your base board, so that may increase the current requirements.
3.3V output
Maximum 5% voltage drop
100 mV peak-to-peak ripple maximum
500 mA minimum output current at 3.3V recommended for future compatibility
Maintain these values at no-load as well as maximum load
