nrf52 Low temperature issue

[jayesh]

I am using nRF52832 with SDK 11.0.0 and S132_V2.0.0 for my application. My beacon is inside Refrigerator where temperature varies from -2 to 20 degree.My Beacon code is in Pheripheral mode.

I have found following issue with my hardware.

If I put hardware in Refrigerator then I found that at low temperature(< 0 degree) after some time advertisement goes off. If I took out hardware out of cooler then after some time it starts advertisement again. Please note I have enabled internal DC to DC converter in nRF52. One thing i have done that i have disable DC to DC converter and test again in cooler then advertisement doesn't go off and works ok. But that to is not 100% reliable.

Same thing when i try with third party nRf51 module all is working good. I am keeping both nRf51/52 Beacons inside refrigerator. After sometime nRf52 stops advertising but nRf51 is working good whole day at +-2 Degree celsius.

Now when i expose this nRf52 hardware at room temperature then its working good. Its advertising as well as connecting whole day.

So i am bit confuse why this thing is not working at 0 degree celsius, Since as per data sheet it should work upto -40 degree celsius.

Even all the components which i have used in this Beacon Hardware all can work upto -40 to 75 degree celsius.

A quick reply would be quite helpful..

[jayesh]

Hi Aryan,

I have read the content of FICR resistor keeping my Beacon in debug mode. I an attaching Screenshot of FICR structure Watch window.

I am using 32MHz crystal for our Custom BLE module and 32 KHz for MCU.

For enabling DC - DC converter i am enabling DCDCEN register. I am using below line in my Initialization code for Enabling it

NRF_POWER->DCDCEN = (POWER_DCDCEN_DCDCEN_Enabled << POWER_DCDCEN_DCDCEN_Pos);

For disabling DC DC i am just commenting DCDCEN register line since by default DC DC mode is disabled.

Even i have tested this thing with 3 to 4 nRf52 Beacon board but same thing happens.

[RK]

12pF may or may not be correct, sounds like the board works fine at room temperature. You can do the maths to work out whether 8pF or 12pF is correct for your crystal. However .. one thing which will change with temperature is the capacitance of those capacitors, and the smaller they are, the more effects there may be.

Normally I thought that capacitance decreased with decreasing temperature, which ought to push the capacitance back down towards 8pF which you'd think would be more correct, however it's possible that if your crystal and loading capacitors are right on the edge of spec both for capacitance and ESR, as you cool the board perhaps the changes push it out of spec and the 32MHz crystal stops working. Or possibly the 32kHz crystal stops working, you should look at that too.