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MPC5644A eQADC ch 128 not returning valid temperature sensor value

Question asked by William Troy Jr on Apr 21, 2015
Latest reply on Apr 22, 2015 by William Troy Jr

I am trying to get the MCU temperature on an

 

SPC564A70L7

 


TTSENS_CODE(TLOW) is 0x1647(-40C)

TTSENS_CODE(THIGH) is 0x1D61(150C)

VBG_CODE(TLOW) is 0xF7F

Temperature sensor is ch 128 and returns values roughly 0x16A0 at room temperature/normal running.

Bandgap is ch 45 and returns values roughly 0x1000.


When temperature formula is applied (MPC5644ARM pp 1231), (TTSENS_CODE(T) X B) calculates to a value less than TTSENS_CODE(TLOW) which should be impossible. The reading from ch 128 when bandgap adjusted is below the -40C value. What is wrong?


eQADC is calibrated and works just fine reading various internal voltage and the bandgap.

 


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