n

TEMP

V

ADC Code

2

FSR

§

·

u

¨

¸

©

¹

TMP63

TEMP

BIAS

BIAS

TMP63

R

V

V

R

R

§

·

u ¨

¸

©

¹

R

Bias

V

Bias

R

TMP63

C

Filter

R

Filter

IN

IN

REF

GND

ADC

11

TMP63-Q1

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Typical Application (continued)

(negative or positive). Alternatively, the thermistor can be biased directly using a precision current source

(yielding the highest accuracy and voltage gain). It is common to use a voltage divider with thermistors because

of its simple implementation and lower cost. The TMP63-Q1 has a linear positive temperature coefficient (PTC)

of resistance such that the voltage measured across it increases linearly with temperature. As such, the need for

a linearization circuits is no longer a requirement, and a simple current source or a voltage divider circuit can be

used to generate the temperature voltage.

This output voltage can be interpreted using a comparator against a voltage reference to trigger a temperature

trip point that is either tied directly to an ADC to monitor temperature across a wider range or used as feedback

input for an active feedback control circuit.

The voltage across the device, as described in Equation 2, can be translated to temperature using either a

lookup table method (LUT) or a fitting polynomial, V(T). The Thermistor Design Tool must be used to translate

Vtemp to Temperature. The temperature voltage must first be digitized using an ADC. The necessary resolution

to the reference voltage of the ADC to create a measurement where the difference in tolerance between the bias

voltage and the reference voltage cancels out. The application can also include a low-pass filter to reject system

level noise. In this case, place the filter as close to the ADC input as possible.

8.2.1.2 Detailed Design Procedure

the voltage supply are canceled and do not affect the temperature accuracy (as shown in Figure 15) . Equation 2

is given in Equation 3.

Figure 15. Voltage Divider With an ADC

(2)

where

•

•

n is the resolution of the ADC

(3)