nRF52823 HFXO DC specificaiton

[JGP_Kenji]

Hiya,

Regarding voltage amplitude peak to peak for external high-swing clock HFXO 32MHz, what's supply rails？I don't find out this specification defined in datasheet PS_V1.2.

Thanks Kenji

[JGP_Kenji]

Hi Jorn,

I'd like to know the specification for HFXO 32MHz likes Vamp_in_xo_low defined in datasheet for LFXO 32.768KHz

Thanks Kenji

[Jørn]

Unfortunately we do not have any numbers for that, as the HFCLK is not designed to receive a clock signal from an external source. The LFCLK is specifically designed to be able to receive a clock signal from an external oscillator, which is why those numbers are included in the specification.

[JGP_Kenji]

More confusion for me.

The section of Nordic nRF52832 datasheet, Clock - clock control, there are two signal sources to HFLCK in the block diagram, HFINT internal oscillator and HFXO Crystal oscillator.

However, I saw "The HFXO is started by triggering the HFCLKSTART task and stopped using the HFCLKSTOP task. A HFCLKSTARTED event will be generated when the HFXO has started and its frequency is stable"

All in all, my understanding is HFXO must be running to use RADIO and NFC module, I have designed those wireless functions in product and just would like to know the input voltage level of HFXO Crystal oscillator, not HFCLK.

But you mentioned HFCLK isn't designed to receive a clock signal from an external source,which mean HFXO crystal oscillator in chip isn't working in fact？The only clock signal to HFCLK, is HFINT？

Pls. clarify if any.

Thanks Kenji

[Jørn]

I may have worded my previous message a bit clumsily, I apologize for that. The HFCLK receives its clock signal from 1 of 2 sources. The internal RC oscillator (HFINT), or the internal crystal oscillator (HFXO). Both are located on-chip. An external crystal is necessary for the internal crystal oscillator to run. The crystal oscillator's power supply is located on-chip and it is not necessary to supply it with voltage. All that is needed is a quartz crystal within the specifications stated in the product specification, along with appropriate tuning capacitors.

What I meant by external sources is you cannot supply a 32MHz signal from an external, off-chip, oscillator.

I struggle with understanding what the supply voltage you mention is. You do not need to supply any voltage other than VDD, as stated in the reference schematics.

[JGP_Kenji]

It's good we aligned partly, and I knew Crystal doesn't need to be supply any voltage externally.

How to make sure the external crystal 32MHz works in accordance with Nordic's specification when RADIO is running？The way I figured out is to identify the numbers of peak-to-peak voltage of clock signal inputted to XC1, that's why I need those numbers of voltage level.

Besides, I assumed internal crystal oscillator on-chip is a prefect driver to drive external crystal 32MHz,

Thanks