nRF54 UART connection failure at low temperature

[Brutus]

Dear Nordic team,

We are using the nRF54L15 QFN52 package on our custom device and are using the P0.06 and P0.00 for the TX and RX, respectively, for our UART service interface. When testing our device in a climate chamber, we noticed that the UART connection was lost at around -18°C. As the operating temperature of the SoC goes down until -40°C, we didn't expect the UART to fail at -18°C. Would you have any clue to why this happened and how we can avoid it?

We submit a design review with our schematics. Case ID: 354184

Thank you in advance for your time and consideration.

Best regards,

Federico

[JONATHAN LL]

Hi,

Are you using the external crystal as source, have you tested with internal HFINT and does the issue persist if so?

What crystal, can you share the datasheet. 

Have you probed the TX pin during the connection loss? or done any other debugging steps?

What does the test setup look like? is the UART service interface also in the temp chamber? 


Regards,
Jonathan

[Brutus]

Hi Jonathan,

for the HF crystal, we are using ABM11W-32.0000MHZ-8-D1X-T3 from Abracon 5556.ABM11W.pdf

For our test setup, we connected 2 probes, 1 on the TX and 1 on the RX, to the oscillator, and saw that the TX line leaving the nRF went flat once the -18°C threshold was reached.

Only our board with the nRF is in the climate chamber and the UART lines are brought outside of the chambre, so the UART to USB is always at room temp.

I'll try to disable the external crystal and use only the internal one