TMP61

BIAS

TMP61

BIAS

n

n

TMP61

BIAS

TMP61

BIAS

R

V

R

+ R

R

ADC Code

2

2

V

R

+ R

§

·

u ¨

¸

§

·

©

¹

¨

¸

©

¹

n

TEMP

V

ADC Code

2

FSR

TMP61

TEMP

BIAS

TMP61

BIAS

R

V

V

×

R

+ R

§

·

¨

¸

©

¹

12

TMP61

SBOS921 – DECEMBER 2018

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Product Folder Links: TMP61

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Copyright © 2018, Texas Instruments Incorporated

Typical Application (continued)

It is common to use a voltage divider with thermistors because of its simple implementation and lower cost. The

TMP61, on the other hand, 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 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, 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 TMP61 can be translated to temperature using either a lookup table method (LUT) or a

fitting polynomial, V(T), as described in Equation 3. The temperature voltage must first be digitized using an

ADC. The necessary resolution of this ADC is dependent on the biasing method used. Additionally, for best

where the difference in tolerance between the bias voltage and the reference voltage are cancelled. A low-pass

filter may also be implemented to reject system level noise, and should be placed as close to the ADC input as

possible.

9.2.1.2 Detailed Design Procedure

the voltage supply will be canceled and will not affect the temperature accuracy. This type of configuration is

range, and ADC resolution is given in Equation 4.

Figure 12. TMP61 Voltage Divider with an ADC.

(3)

where

•

•

n is the resolution of the ADC

(4)

(5)