Component out-of-spec and EOL

[bartbok]

Hi,

I am building the AirCube and thank you for sharing all the information.

When I was going over the BOM to order the components I noticed one issue:

The component C9 (47uF capacitor in 0603 package) is rated for 2.5V and used in the 3.3V supply rail to the ESP32. Using a ceramic capacitor above its rated voltage will in-time result in breakdown and a potential short circuit of this capacitor. Additionally, the effective capacitance drops significantly when you use the capacitor above the rated voltage. If you want this large capacitance, you will have to select either a larger package (i.e. 0805/1206/1210) or place multiple smaller in parallel. Since the datasheet of the ESP32 specifies in the typical application diagram a 10uF capacitance where you used to 47uF, I think selecting a smaller capacitance of 10uF in 0603 package with 10V rating and X7R dielectrics is sufficient. I use PN: GRM188Z71A106KA73D.

Besides that:

1. the AP2120N-1.8TRG1 (U5) is end-of-life, I selected the MCP1700T-1802E as a drop-in replacement but I still need to test.
2. the availability of AP2205-33W5-7 (U6) in Europe is limited at the moment, I selected the XC6201P332MR-G as a drop-in replacement despite not having an enable option