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QD2/4: how much reads the internal temperature sensor @ 5V, 115°C ???

Question asked by Emil Kovatchev on Oct 21, 2009
Latest reply on Oct 22, 2009 by Emil Kovatchev

Hello everyone!


Being quite happy with the QD2 (which controls a demanding automotive application in my design), I have one last question.


In order to protect the electronics, the QD2 must shut down, as soon as the PCB surface temperature exeeds 115°C. Some +-18°C tolerancies are allowed.


The internal temp sensor seems to be a perfect match for this task, however I cannot find any data (graphs, tables) saying how much would the ADC read at Vdd = 5V and 115°C.


I am out of flash and cannot apply the calibration procedure described in AN3031. And I don't really need it, because I don't want to measure the whole temp. range, but just need a single point (ADC reg. content), corresponding to the 115°C, if the ADC reading goes below that threshold, I'd just shut down.


Unfortunately, the charts in AN3031 are  for Vdd up to 3.6V and a simple extrapolation won't work (already checked this, I guess the proper ADC value is somewhere about 200 for S9S08QD2 and ~100°C, which by no means matches the data from AN3031).


And I don't really want to spend my time in the thermal chamber, heating the µC up to 115° and trying to get the corresponding ADC reading  thru the BDM interface. 


Does anybody have an idea, where can I get those data?


Many thanks!