Is an external crystal for the LFCLK strongly recommended for products that will be used in environments ranging from -40 °C to 60 °C?

[Aurele]

Hello,

Our current design does not use an external crystal for the LFCLK. As a consequence, I configured the LFCLK to use the RC oscillator. We also have power consumption constraints, so I cannot use the Synth option (I noticed that it doubles the power consumption when using BLE only).

Our product needs to operate reliably in environments ranging from -40 °C to 60 °C, and I have doubts about BLE performance in such conditions, even if I enable RC source recalibration every X seconds.

So my question is: should I push the team to use an external crystal for the LFCLK?

Regarding the HFCLK, we are already using an external crystal.

Thank you in advance,

Regards,
Aurélien

[Priyanka]

Hi,

Yes, I would suggest you to use an external crystal for the LFCLK because given that there is a lot of temperature changes and also preiodic changes, the internal RC oscillator might have lesser accuracy and might also be susceptible to the temperature changes. Moreover, there are chances that the RC oscillator's frequency drift during the temperature changes can impact BLE performance.

Also, using the synthesized LFCLK (from HFCLK) is not recommended for low-power BLE applications because this can increase the current consumption. So given all the factors, it would be better to go for an external crystal.

-Priyanka

[Aurele]

Hi

OK, understood. Thank you very much for the reply :)

Best regards,