J

A

JA

DD S

DD

O

L

T = T +

(V I ) + (V

- V ) I

T

ª

º

¬

¼

(-5.50 mV /

V =

T + 1035 mV

(-5.50 mV /

V - 925 mV =

(T - 20

760 mV - 925 mV

50

u

¹

·

V - 925 mV =

(T - 20

u

¹

·

ª

º

ª

º

«

»

«

»

¬

¼ ¬

¼

2

TEMP

2

mV

mV

V

mV = 870.6mV - 5.506

T - 30°C

- 0.00176

T - 30°C

°C

°C

LMT84, LMT84-Q1

SNIS167A – MARCH 2013 – REVISED JUNE 2013

www.ti.com

Although the LMT84/LMT84-Q1 is very linear, its response does have a slight umbrella parabolic shape. This

shape is very accurately reflected in Table 1. The Transfer Table can be calculated by using the parabolic

equation.

(1)

For a linear approximation, a line can easily be calculated over the desired temperature range from the Table

using the two-point equation:

(2)

coordinates of the highest temperature.

For example, if we want to resolve this equation, over a temperature range of 20°C to 50°C, we would proceed

as follows:

(3)

(4)

(5)

Using this method of linear approximation, the transfer function can be approximated for one or more

temperature ranges of interest.

MOUNTING AND THERMAL CONDUCTIVITY

The LMT84/LMT84-Q1 can be applied easily in the same way as other integrated-circuit temperature sensors. It

can be glued or cemented to a surface.

To ensure good thermal conductivity, the backside of the LMT84/LMT84-Q1 die is directly attached to the GND

pin (Pin 2). The temperatures of the lands and traces to the other leads of the LMT84/LMT84-Q1 will also affect

the temperature reading.

Alternatively, the LMT84/LMT84-Q1 can be mounted inside a sealed-end metal tube, and can then be dipped

into a bath or screwed into a threaded hole in a tank. As with any IC, the LMT84/LMT84-Q1 and accompanying

wiring and circuits must be kept insulated and dry, to avoid leakage and corrosion. This is especially true if the

circuit may operate at cold temperatures where condensation can occur. If moisture creates a short circuit from

often used to ensure that moisture cannot corrode the leads or circuit traces.

The thermal resistance junction to ambient (

temperature due to its power dissipation. The equation used to calculate the rise in the LMT84/LMT84-Q1's die

temperature is:

(6)

2

μA, the junction temperature would be 30.0146°C, showing a self-heating error of only 0.014°C. Since the

LMT84/LMT84-Q1's junction temperature is the actual temperature being measured, care should be taken to

minimize the load current that the LMT84/LMT84-Q1 is required to drive. Table 2 shows the thermal resistance of

the LMT84/LMT84-Q1.

Table 2. LMT84/LMT84-Q1 Thermal Resistance

DEVICE NUMBER

PACKAGE NUMBER

THERMAL RESISTANCE (

LMT84DCK

DCK0005A

415°C/W

8

Submit Documentation Feedback

Copyright © 2013, Texas Instruments Incorporated

Product Folder Links: LMT84 LMT84-Q1