Sharing a 32kHz crystal between 2x nRF52840

RE: Sharing a 32kHz crystal between 2x nRF52840

Eggz — Tue, 30 Jul 2019 14:06:54 GMT

Hi Simon,

Thanks. I will close this question.

RE: Sharing a 32kHz crystal between 2x nRF52840

Simonr — Tue, 30 Jul 2019 13:46:12 GMT

Hi Egil

One of the nRF52840s will have to stay in power on mode but should be able to run the crystal from the Low-power mode. So yes, there will be an increased power consumption on one of them, but not by too much I think.

Best regards,

Simon

RE: Sharing a 32kHz crystal between 2x nRF52840

Eggz — Tue, 30 Jul 2019 08:43:00 GMT

Hi Simon,

Thanks! I'm afraid I'm not familiar with the nRF9160. I was referring to the last sentence in the conclusion in the whitepaper, where nRF24L01 is said to have this limitation. The whitepaper recommends us to control the LF crystal with the external MCU & to feed the nRF24L01. In our case we have 2x nRF52840 and no external MCU, so the crystal must be controlled by one of them, which may lead to increased power consumption.

Best regards,

RE: Sharing a 32kHz crystal between 2x nRF52840

Simonr — Tue, 30 Jul 2019 08:17:26 GMT

Hi Egil

Sorry, but can you please explain what you mean with "power up as input pin". If you mean an enable pin like on the nRF9160, then no.

Best regards,

Simon

RE: Sharing a 32kHz crystal between 2x nRF52840

Eggz — Mon, 29 Jul 2019 16:47:41 GMT

Hi Simon,

Thanks - very informative whitepaper.

In our case we have 2x nRF52840, so one of them will have to control the crystal. Does nRF52840 have power up as input pin? The whitepaper covers nRF24L01 which didn't have this option.

Best regards,

RE: Sharing a 32kHz crystal between 2x nRF52840

Simonr — Mon, 29 Jul 2019 13:49:52 GMT

Hi Egil

Please check out our whitepaper on Sharing crystal with an MCU.

Best regards,

Simon