Temperature Range

Linear Equation

V

Maximum Deviation of Linear Equation from

Parabolic Equation (°C)

T

T

−55

+130

−11.79 mV/°C × T + 1.8528 V

±1.41

−40

+110

−11.77 mV/°C × T + 1.8577 V

±0.93

−30

+100

−11.77 mV/°C × T + 1.8605 V

±0.70

-40

+85

−11.67 mV/°C × T + 1.8583 V

±0.65

−10

+65

−11.71 mV/°C × T + 1.8641 V

±0.23

+35

+45

−11.81 mV/°C × T + 1.8701 V

±0.004

+20

+30

−11.69 mV/°C × T + 1.8663 V

±0.004

FIGURE 2. First Order Equations Optimized For Different Temperature Ranges.

2.0 Mounting

The LM19 can be applied easily in the same way as other

integrated-circuit temperature sensors. It can be glued or ce-

mented to a surface. The temperature that the LM19 is sens-

ing will be within about +0.02°C of the surface temperature to

which the LM19's leads are attached.

This presumes that the ambient air temperature is almost the

same as the surface temperature; if the air temperature were

much higher or lower than the surface temperature, the actual

temperature measured would be at an intermediate temper-

ature between the surface temperature and the air tempera-

ture.

To ensure good thermal conductivity the backside of the

LM19 die is directly attached to the GND pin. The tempertures

of the lands and traces to the other leads of the LM19 will also

affect the temperature that is being sensed.

Alternatively, the LM19 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 LM19 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 conden-

sation can occur. Printed-circuit coatings and varnishes such

as Humiseal and epoxy paints or dips are often used to ensure

that moisture cannot corrode the LM19 or its connections.

The thermal resistance junction to ambient (

θ

rameter used to calculate the rise of a device junction tem-

perature due to its power dissipation. For the LM19 the

equation used to calculate the rise in the die temperature is

as follows:

T

where I

the output. Since the LM19's junction temperature is the ac-

tual temperature being measured care should be taken to

minimize the load current that the LM19 is required to drive.

The tables shown in Figure 3 summarize the rise in die tem-

perature of the LM19 without any loading, and the thermal

resistance for different conditions.

TO-92

TO-92

no heat sink

small heat fin

θ

JA

T

θ

JA

T

(°C/W)

(°C)

(°C/W)

(°C)

Still air

150

TBD

TBD

TBD

Moving air

TBD

TBD

TBD

TBD

FIGURE 3. Temperature Rise of LM19 Due to

Self-Heating and Thermal Resistance (

θ

3.0 Capacitive Loads

The LM19 handles capacitive loading well. Without any pre-

cautions, the LM19 can drive any capacitive load less than

300 pF as shown in Figure 4. Over the specified temperature

range the LM19 has a maximum output impedance of 160

Ω. In an extremely noisy environment it may be necessary to

add some filtering to minimize noise pickup. It is recommend-

ed that

supply voltage, as shown in Figure 5. In a noisy environment

it may even be necessary to add a capacitor from the output

to ground with a series resistor as shown in Figure 5. A 1

μF

output capacitor with the 160

Ω maximum output impedance

and a 200

Ω series resistor will form a 442 Hz lowpass filter.

Since the thermal time constant of the LM19 is much slower,

the overall response time of the LM19 will not be significantly

affected.

20004015

FIGURE 4. LM19 No Decoupling Required for Capacitive Loads Less than 300 pF.

5

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