TX Carrier frequency offset

[Frederic]

We are in process to certified a product using the nrf52832. While testing the certification team find an offset greater than 20 ppm, like in the following scree shot:

(2 402 058 [Hz] - 2 402 000 [Hz]) / 2 402 000 [Hz] = 24.1 e-6

12pF capacitors are used on a 32MHz crystal with load capacitance of 10pF. The 32 MHz crystal frequency tolerance is +/-10ppm at +25°C, +/-20ppm between -20°C and +70°C.

Is this level of accuracy is possible with the nrf52832?

Thank you for your help!

[Jay Tyzzer]

Hi Frederic,  Have you tried using either a 32MHz crystal with a CL value of 8pF or.. the current Crystal but with 15pF load caps?   

Load cap value = (CL*2) - (PinCap + Stray Cap)  So figure (10*2) - (4+1) = 15.   

Pin capacitance is 4pF and maybe 1pF for stray capacitance. 

Which ever is easier to change out...

[Frederic]

In the 19.4.2 64 MHz crystal oscillator (HFXO) table in the nrf52832 datasheet what exactly the C0 (7,5,3 pF) in the RS_HFXO_7PF, RS_HFXO_5PF, RS_HFXO_3PF values means? Is it the load capacitance of the crystal?