nRF52833 LFXO question

RE: nRF52833 LFXO question

Jared — Mon, 25 Oct 2021 09:44:56 GMT

I think that should be fine. We haven't specified the current consumption with an external LFXO source but for a LFXO crystal it's ca 0.23 µA. I believe it should be somewhat similar for your case.

RE: nRF52833 LFXO question

harrykuang — Fri, 22 Oct 2021 14:56:02 GMT

Thanks Jared

Any concerns with using a MEMS 32.768 Khz oscillator? This one is 3ppm. Looks like it can only drive 50uA of output current. I am thinking the nRF LFXO input does not consume nearly this much current?

Harry

RE: nRF52833 LFXO question

Jared — Fri, 22 Oct 2021 09:30:24 GMT

Hi,

The nRF52833 has a +- 500 ppm requirement for the LFXO crystal for the BLE stack. The requirement for the ANT stack is even more strict at +-50 ppm.

If we calculate the allowed variation for the LFXO crystal for the BLE stack:

32.768 +- (32.768 x 500/10^6) = 32.784384 and 32.751616.

For the oscillator:

32.875 +- ( 32.875 x 5/10^6) = 32.87516438 and 32.87483563

The oscillator is therefore not within the allowed variation for the LFXO crystal.

[quote user=""]Is the absolute frequency a deal breaker here?[/quote]

Yes.

best regards

Jared