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10 February 2015 10:58 AM

bonmot Newbie

Total Posts: 13

Joined 2013-01-09

When enabling softdevice in Nordic nRF51422, you can set LFCLK crystal oscillator accuracy from 20PPM to 500PPM.

We are evaluating the BOM cost, also sensitive to the battery life. So I need a little more info for the part decisions.

I believe better accuracy will set the "allowed timing error" shorter in the softdevice, which saves power.

My question is: Is there a rough formula I can use to calculate the time difference between different accuracy settings?

Thanks

Paul

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BLE and ANT Developer using Nordicsemi nRF51422, ON, Canada

19 February 2015 11:27 AM #1

usamak Sr. Member

Total Posts: 156

Joined 2013-01-07

Hi Paul,

The ANT protocol has a frequency tolerance requirement of ±50ppm. So for ANT applications on the nRF51 you are limited to the 20, 30 and 50 ppm accuracy options (Refer to the nRF51422 Product Specification Document). I would assume the time difference between those accuracy options is minimal, do you have very specific timing/battery requirements for your design?

For reference, the N5 ANT SoC Module from Dynastream Innovations uses a 50ppm 32k crystal.

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How is Crystal PPM setting going to affect the battery life

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