Temperature coefficient of ADC in nRF51822

[diode]

I am wondering where I can find the temperature dependent behavior of the ADCs on nRF51822. I observe the ADC readings vary noticeably even when the die temperature reading shows difference of only 4 degree Celsius. I am trying to figure out whether the variation is from nRF51822 itself or external circuit, assuming that the die temperature reading is accurate enough. Knowing the temperature behavior of ADC (such as the reference voltage) can be very useful.

[Stefan Birnir Sverrisson]

Hi

In the nRF51822_PS v3.1, table 51, it is stated that the maximum voltage drift of internal VBG voltage is 200ppm per degree Celsius. That is voltage drift of 0.08% maximum for 4 degrees Celcius, which is 1024*0.0008 = 0,82 bit maximum difference if you are sampling with 10-bit resolution. So you could see a one bit change by changing temperature with 4 degrees Celcius, it would still be within specification.

[Stefan Birnir Sverrisson]

1.20 V bandgap voltage should be at 25 deg C