LFSYNTH additional current and accuracy

[rgrr2]

Hi

in our device, HFXO is running permanently.  There is an external LFXO running permanently as well.

Now I'm wondering what would be the additional current draw if we switch from NRF_CLOCK_LF_SRC_XTAL to NRF_CLOCK_LF_SRC_SYNTH.  Any data available about this?

Because our application depends on an accurate LFCLK: how actually is LFSYNTH generated from HFCLK?

Thanks for help

Hardy

[Simonr]

Hi

I see. If a large temperature deviation is expected, you might want to adjust the loading. The drift is indicated by the "Parabolic coefficient" parameter in the datasheet. Seeing as the LFSYNTH draws notably more current than the LFXO, I would still suggest using the LFXO, and if necessary you can add either a timer from HFXO or some further steps to compensate for the expected drift. You might also be able to find a 32.768 kHz crystal that has less temperature drift than the one you're looking at.

Best regards,

Simon

[rgrr2]

Many thanks for your help.  So I will have a deeper look in my code if there are periods where a TIMER is enabled and check if I can use it for LFXO calibration/compensation.

Other crystals are actually not a solution, because cost matters.  And BTW the current one is not too bad: it has -0.034 · 10-6 / °C2 typical

Hardy