nRF52832: Frequency tolerance requirement for ANT stack for an extern 32.768kHz crystal oscillator

[drexler_geyer-electr5onic]

The frequency tolerance for ANT stack for an external 32.768 kHz crystal oscillator should be +/- 50 ppm max.

Does it mean over temperature range?

There was the same question for an BLE stack, and I understand that the tolerance is over temperature. For BLE  the required tolerance is +/- 250ppm.

But  to find a crystal +/- 50ppm for a Temperature until 85°C is not possible, because the 'Parabolic coefficient' is about 0,035 ppm/°C^2.

And from 25°C to 85°C there are a delta of 60°C (85-25=60), and it menas 60°C x 60°C x 0,035 = 126ppm.

126ppm is much greater than 50ppm.

So it seems there can not be find a crystal to use the  nRF52832 for ANT, because there is always a requirement for a device over Temperature..

I sit true?

best regards

Josef

[Kenneth]

Hi,

For ANT it is fixed 50ppm, for BLE it is configurable from 1 - 500ppm depending on the LFCLK source. However, this tolerance should be ensured over the entire temperate range you want your product to operate (which may be lower than the 85degree the IC can support). 

I can find the the XO used on the nRF52-DK is: 

XTAL_3215

Epson Toyocom

FC-135 32.768KHZ ±20PPM,9.0PF

Best regards,
Kenneth

[drexler_geyer-electr5onic]

Thank you for your quick answer. 

Best regards

drexler_geyer-elöectr5onic