ESP32-D0WD-V3: External 32 kHz Crystal?

[expresspotato]

Hello,

I'm looking to add a 32.768 Khz crystal to the ESP32-D0WD-V3 to gain bluetooth light sleep as the power consumption is quite high, much higher than WiFi with light sleep.

The design specifications sheet doesn't specify what resistor / capacitor values to put exactly, it's specified as TBD.

The schematic for the WROVER-KIT has the two needed capacitors (C17 & C18) as 12 pF.

Does anyone have experience with this in volume for a reliable external 32.768 kHz oscillator?

[ESP_Sprite]

As it says: the capacitors should be configured according to the load capacitance of the crystal. Specifics are e.g. here.

[expresspotato]

Thanks for the reply. So according to that Adafruit calculation:

CL = (C1 * C2) / (C1 + C2) + Cstray

12.5 pF = (15pf * 15pF) / (15 pF + 15 pF) + 5 CStray
12.5 pF = (19pf * 19pF) / (19 pF + 19 pF) + 3 CStray

Looks like they should be in the range of 15 to 19 pF depending on CStray.