Multiple NRF24L01P single clock oscillator

[IlyaZ]

Hello,

Our application board uses two NRF24L01P and two microcontrollers, so we have total four quartz generators on board. To simplify things we would like to use a single clock oscillator KXO-V97 by Geyer with the following characteristics:

frequency stability +-50ppm symmetry 50% ± 10% at ½ Vcc level rise & fall time max. 6 ns voltage 3,3V random jitter 7ps max. peak to peak jitter 40ps max.

Can you please suggest is this possible and can NRF24L01P work in such configuration without compromising its performance?

Best regards

Ilya Zakharov

[MartinBL]

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

[IlyaZ]

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?

[MartinBL]

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