32 Khz square wave in Lieu of Crystal

[WesC]

In one of the customers current design implementations, they use a 32.768 kHz square wave in lieu of a 32.768 kHz crystal. they reduce the peak-to-peak amplitude and capacitor couple it to the crystal input, allowing the on-board crystal drive circuit to establish the DC bias.

 

Would the nRF52 part support this design approach, or does the part require a crystal to be used?

[Jared]

Hi Wes,

The nRF52840 supports using external clock such as a RTC for the LFCLK, it but the Softdevice does not, as we do not test this combination with the Softdevice. 

regards

Jared

[WesC]

Thanks for the Reply.

I know you mentioned this has not been tested, but what is the reason the softdevice would not work with the RTC or other external source? (other than a 32Khz Crystal) 

wes

[Jared]

Hi Wes,

First, is the customer using the Softdevice Controller or the Softdevice from nRF5SDK?

On a second thought, I might have given you an outdated answer.

regards

Jared

[WesC]

They would be using the Softdevice Controller and NCS

[Jared]

Hi Wes,

It's supported in NCS, 

I'm sorry for my earlier statement about it not being supported. 

regards

Jared