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

[Jørn]

Hello JGP_Kenji

Unfortunately the high frequency clock (HFCLK) of the nRF52 series does not support use of an external clock source. The only valid sources for HFCLK are the internal oscillator, or the 64MHz crystal oscillator. Do note that the crystal oscillator must be running for the RADIO and NFC modules to work.

EDIT:

The following comment was supplied by our designers

Based on simulations the peak-to-peak oscillation amplitude on XC1 and XC2 can range from appx. 0.3V to appx. 1.1V, depending on crystal selection, load capacitors, process variation, operating temperature and supply voltage. The amplitude is usually slightly bigger on XC2 than on XC1. The DC offset is typically around 0.5V. When doing voltage measurements on XC1 and/or XC2 it's important to use a low-capacitance active probe. A regular passive probe will add too much load capacitance. The probe should also have an input resistance of at least 10Mohm.

In order to verify that the load capacitors are optimal, it's best to measure TX carrier frequency.

Best regards

Jørn Frøysa

[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