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How to interface NTC thermistor to Kinetis ADC input

Question asked by Dennis Hicks Employee on Jan 18, 2017
Latest reply on Jan 21, 2017 by Hui_Ma

Hello,

 

I have a circuit with 100K thermistor in series with 25k resistor to ground. I connect my adc input to the point where

the thermistor and resistor connect and also a capacitor. This approach works on some adc channels but not others.

 

reading through the datasheet I notice there is an internal adc resistance of 5k Ras. So it appears having a high impedance input circuit may be an issue.

 

Is there a reliable way to make this approach work ?

 

On some of the eval boards like the FRDM-KL03z I notice they use lower value 10k NTC with 5k above and 5k below in series with 2 adc channels. Why do they do this as compared to approach above.

 

Regards,

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