NC

GND

Vo

GND

NC

V+

NC

GND

Vo

GND

V+

LM20

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SNIS106Q – DECEMBER 1999 – REVISED JANUARY 2015

9 Power Supply Recommendations

The LM20 has a very wide 2.4-V to 5.5-V power supply voltage range that makes ideal for many applications. In

noisy environments, TI recommends adding at minimum 0.1

μF from V+ to GND to bypass the power supply

voltage. Larger capacitances maybe required and are dependent on the power-supply noise.

10 Layout

10.1 Layout Guidelines

The LM20 can be easily applied in the same way as other integrated-circuit temperature sensors. It can be glued

or cemented to a surface. The temperature that the LM20 is sensing is within approximately 0.02°C of the

surface temperature to which the leads of the LM20 are attached.

Implementing the integrated-circuit temperature sensors 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 temperature between the surface temperature and

the air temperature.

To ensure good thermal conductivity, the backside of the LM20 die is directly attached to the pin 2 GND. The

temperatures of the lands and traces to the other leads of the LM20 will also affect the temperature that is

sensed.

Alternatively, the LM20 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 LM20 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. Printed-circuit coatings and varnishes such as a conformal coating

and epoxy paints or dips are often used to ensure that moisture cannot corrode the LM20 or its connections.

10.2 Layout Examples

Figure 11. Layout Used for No Heat Sink Measurements

Figure 12. Layout Used for Measurements With Small Heat Sink

10.3 Thermal Considerations

temperature due to its power dissipation. For the LM20, the equation used to calculate the rise in the die

temperature is as follows:

where

•

the actual temperature being measured, take care to minimize the load current that the LM20 is required to

drive.

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