LFXO drive from an RTC

[aarondashine]

Hi,

I have read a few support tickets but want to make sure I am understanding correctly. I am using the nrf52840 with nrf Conect SDK 2.5.0 and want to use an RTC square wave output as the source for LFXO. From the product specification the nrf52840 will support this as an input - 'Rail-to-rail clock signal applied to the XL1 pin', however some other threads suggest the BLE will not work in this configuration. Can you confirm if this is correct?

Thanks

Aaron

[Menon]

Hello,

I wanted to let you know that I have been assigned to this case and have started looking into it. I will get back to you soon, probably tomorrow.

Kind Regards,

Abhijith 

[Menon]

Hello,

Sorry the long response time I am taking.

I have read a few support tickets but want to make sure I am understanding correctly. I am using the nrf52840 with nrf Conect SDK 2.5.0 and want to use an RTC square wave output as the source for LFXO. From the product specification the nrf52840 will support this as an input - 'Rail-to-rail clock signal applied to the XL1 pin',

Yes, it is true that you can use an external rail-to-rail clock signal applied to the XL1 pin as a source for the low-frequency crystal oscillator (LFXO). See the section LFCLK controller.

however some other threads suggest the BLE will not work in this configuration. Can you confirm if this is correct?

I am also not sure about this, as I am not a BLE expert. So I have asked some of my colleagues about this, but it's a holiday week in Norway, and I couldn't get a concrete answer to share, which is why I am taking some time here. But have you tested your application with any specific configuration and it's crashing? If so, please share the details here. 

I will try to update you soon.

Kind Regards,

Abhijith