nRF52832 External HFXO

[hank2k]

As your datasheet, External HFXO's Run current is 250uA, but HFINT case is 60uA. Despite lager current, why do you use HFXO in reference circuit?

I would like to use HFINT instead of HFXO for lower power consumption. Please let me know about your recommendation.

Regards,

[RK]

Because the softdevice requires the HF crystal as the internal RC isn't accurate enough for radio operation. So if you are using bluetooth, you need the external crystal .. from the manual

The HFXO must be running to use the RADIO, NFC module or the calibration mechanism associated with the 32.768 kHz RC oscillator.

[hank2k]

But If that case is running BLE not Bluetooth, do we use HFINT with 32.768KHz RC oscillator?

[MartinBL]

Hi,

It is as RK says. HFXO is only required when you are using the radio or NFC, or when you are doing calibration of the internal low frequency 32kHz oscillator (LFRC). The nRF5s will automatically switch between HFINT and HFXO and choose the most power efficient option (unless you manually start the HFXO). So unless you need to control it yourself you don't need to worry about this at all.

What do you mean by "do we use HFINT with 32.768KHz RC oscillator"? You can choose to use LFRC or LFXO. In this case though, it is actually more power efficient to use an external LFXO.

[RK]

Martin - I think you mixed up HFINT and HFXO in the first paragraph, it's XO you need for the radio and NFC and it's HFXO you manually start if you want it.

[MartinBL]

Oh, I did. Thank you.