NXP Semiconductors Freedom FRDM-KV11Z, User Manual, Page: 12 / 20

Thermistor
FRDM-KV11Z Evaluation Board Users Guide
12 NXP Semiconductors
Figure 11. Accelerometer and magnetometer schematic
7. Thermistor
There is a thermistor circuit on the FRDM board. There is a thermistor RT1 provided on the board that
can be used as single-ended or differential analog inputs to the KV10Z MCU.
In addition to the thermistor, there is a resistor between the thermistor and 3.3 V system power supply
and another resistor between the thermistor and ground. The thermistor is a 10 K ohm part, but the
associated divider chain uses different resistors. This makes the voltage across the thermistor larger or
smaller, and provides the ability to try the different gain settings on the analog channels. The thermistor
circuit is designed to prov ide useable differential inputs over the temperature range of 90˚ C to - 20˚ C.
In addition to the thermistor voltage divider chain, the thermistor has a 0.1 uF capacitor in parallel.
Each analog input to the KV10Z has a 100-ohm series resistor and a 2200 pF capacitor as a low-pass
filter. This helps protect the KV10Z from electrostatic discharge, and lowers the impedance of the
analog signal so that it can be sampled with less noise.