nRF52832 frequency tolerance bluetooth

[eck]

Hi,

I am wondering which frequency tolerance is acceptable for the HFXO, as in the product specification, p.105, a maximum value of +/- 40 ppm for Bluetooth low energy applications is stated, but in the bluetooth core specification a limit for the Radio Frequency Tolerance of +/- 75 kHz (accordingly to about +/- 30ppm) is given. As the radio frequency is generated from the HFXO this two statements are ill-suited, do you have an explanation?

[Øyvind Karlsen]

Hi,

For the BLE physical layer the core spec says:

The deviation of the center frequency during the packet shall not exceed
±150 kHz, including both the initial frequency offset and drift. The frequency
drift during any packet shall be less than 50 kHz. The drift rate shall be less
than 400 Hz/µs.

Meaning that the worst case tolerance should be better than ±100 kHz for the crystal, this corresponds to approximately 40 ppm, which is the maximum usable value stated in the nRF52 datasheet.

The ±75 kHz measure is for BR/EDR (Bluetooth classic) schemes.

Best regards,

Øyvind