nRF52811 : External crystal X2 Oscillator

[Poompat]

Hi,

I have qestion about crystal 32.768 kHz follow schematic as attached file.

nrf52811_qcaa_schematic.pdf

Is it nessary to use ?

Is it possible, Can I remove this crystal ?

Thank you

Best Regards,

[Vidar Berg]

Hi,

It is optional. You can use the internal 32.768 kHz RC oscillator (LFRC) instead. The drawback is slightly increased base current and also increased RADIO RX windows for BLE to account for the lower clock tolerance (500 ppm vs. 20 ppm.

Best regards,

Vidar

Edit: you can use our online power profiler (link) to see how the LF clock source impacts the current consumption.

[Poompat]

Hi,

Many thanks for your answer

For BLE operation, I just mount an external 32 MHz (X1) only for main system and don't mount an external 32 kHz (X2) by using LFRC instead.  Is it enoungh for BLE using ? and my understanding are correct ?

Thank you

Best Regards,

[Vidar Berg]

Hi,

No problem. Yes, you can use BLE without the 32K crystal mounted.