J

A

JA

DD S

DD

O

L

T = T +

(V I ) + (V

- V ) I

T

ª

º

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¼

LMT86, LMT86-Q1

SNIS169C – MARCH 2013 – REVISED OCTOBER 2015

www.ti.com

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

temperature ranges of interest.

8.4 Device Functional Modes

8.4.1 Mounting and Thermal Conductivity

The LMT86 and LMT86-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 LMT86 and LMT86-Q1 die is directly attached to the

GND pin (Pin 2). The temperatures of the lands and traces to the other leads of the LMT86 and LMT86-Q1 will

also affect the temperature reading.

Alternatively, the LMT86 and LMT86-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 LMT86 and LMT86-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

Printed-circuit coatings are often used to ensure that moisture cannot corrode the leads or circuit traces.

junction temperature due to its power dissipation. The equation used to calculate the rise in the LMT86 and

LMT86-Q1 die temperature is:

(7)

temp 30.014°C self-heating error of 0.014°C. Since the LMT86 and LMT86-Q1's junction temperature is the

actual temperature being measured, care should be taken to minimize the load current that the LMT86 and

LMT86-Q1 is required to drive. Thermal Information(1) shows the thermal resistance of the LMT86 and LMT86-

Q1.

8.4.2 Output Noise Considerations

A push-pull output gives the LMT86 and LMT86-Q1 the ability to sink and source significant current. This is

beneficial when, for example, driving dynamic loads like an input stage on an analog-to-digital converter (ADC).

In these applications the source current is required to quickly charge the input capacitor of the ADC. The LMT86

and LMT86-Q1 is ideal for this and other applications which require strong source or sink current.

measured during bench tests. Its typical attenuation is shown in Figure 8 found in the Typical Characteristics

section. A load capacitor on the output can help to filter noise.

For operation in very noisy environments, some bypass capacitance should be present on the supply within

approximately 5 centimeters of the LMT86 and LMT86-Q1.

8.4.3 Capacitive Loads

The LMT86 and LMT86-Q1 handles capacitive loading well. In an extremely noisy environment, or when driving

a switched sampling input on an ADC, it may be necessary to add some filtering to minimize noise coupling.

Without any precautions, the LMT86 and LMT86-Q1 can drive a capacitive load less than or equal to 1100 pF as

shown in Figure 10. For capacitive loads greater than 1100 pF, a series resistor may be required on the output,

as shown in Figure 11.

(1)

For information on self-heating and thermal response time see section Mounting and Thermal Conductivity.

12

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