S9KEAZ128 on-chip temperature sensor

[ferencalexi]

Hello,

We are trying to use the built-in temperature sensor of the TRK-KEA128 dev board, but the values read from the ADC channel doesn't seem to be valid. We are implementing fixed point approximation according to AN3031 - Temperature Sensor for the HCS08 Microcontroller Family​. Can be this document applied to S9KEAZ128 MCU or are there any other resources we couldn't find?

Thanks!

[ferencalexi]

Thank you for your answer!

We are doing about the same steps and measuring 40 C in an office with 20-22 C inside temperature. Reading your conclusion that without proper calibration (which is not an option unfortunately) the error could reach 20 C we probably have to look for other options :smileysad:

[egoodii]

The chip will naturally have its own 'in operation rise' to consider as well.

I use the ADT75 for my temperature-information requirements anywhere I need better than 'gosh, it sure is hot'...  About a buck for the 'A' grade (2C), a little more for 'B' grade (1C).

[ferencalexi]

Actually our goal would be to use as some sort of thermal watchdog, but unfortunately it looks completely unreliable.

[egoodii]

AFAIK all 'formerly Freescale' parts use the same basic on-chip temperature process, with 'slight' variations in 25C voltage and slope(s), as detailed in individual datasheets.  BUT I am NO FAN of AN3031.  You might want to look at my post:

On-chip temperature Calculations