Multiple NRF24L01P single clock oscillator

RE: Multiple NRF24L01P single clock oscillator

MartinBL — Wed, 06 May 2015 12:52:59 GMT

We don't have any documentation on it, but what you describe should work fine.

RE: Multiple NRF24L01P single clock oscillator

IlyaZ — Wed, 06 May 2015 11:11:44 GMT

Thank you for a prompt response! I'm sorry for not being more descriptive, the block diagram shows the real structure with buffers, so load capacitance should not be an issue.

The question is are there specifications regarding frequency stability, 50%-symmetry, rise/fall times and jitter?

RE: Multiple NRF24L01P single clock oscillator

MartinBL — Wed, 06 May 2015 09:32:29 GMT

Hi.

According to this datasheet it looks like the KXO-V79 has a load capacitance of 30pF which is higher than maximum electrical specification at 16pF.

There is a white paper on how to share a crystal with a MCU. It only discuss how to connect two devices, however, but I haven't heard of people connecting more than that. Remember that the radio is very sensitive to crystal frequency fluctuations and connecting four units to one crystal leads to a lot of extra capacitance in traces and IC inputs and probably other unpredictable effects. And keep in mind that there can only be one device that controls the crystal. They can't all start and stop the crystal as they want.

There is also a white paper called Crystal Oscillator Design Considerations that might be of interest.

EDIT: In our nRF24L01+ Evaluation Kit we use a "regular" 16MHz HC49 crystal with tolerance +/-60ppm and CL=12pF