LM35 Precision Centigrade Temperature Sensors
July 1999
LM35
Precision Centigrade Temperature Sensors
General Description
The LM35 series are precision integrated-circuit temperature
sensors, whose output voltage is linearly proportional to the
Celsius (Centigrade) temperature. The LM35 thus has an
advantage over linear temperature sensors calibrated in
˚ Kelvin, as the user is not required to subtract a large con-
stant voltage from its output to obtain convenient Centigrade
scaling. The LM35 does not require any external calibration
or trimming to provide typical accuracies of
±
1
⁄
4
˚C at room
temperature and
±
3
⁄
4
˚C over a full −55 to +150˚C tempera-
ture range. Low cost is assured by trimming and calibration
at the wafer level. The LM35’s low output impedance, linear
output, and precise inherent calibration make interfacing to
readout or control circuitry especially easy. It can be used
with single power supplies, or with plus and minus supplies.
As it draws only 60 µA from its supply, it has very low
self-heating, less than 0.1˚C in still air. The LM35 is rated to
operate over a −55˚ to +150˚C temperature range, while the
LM35C is rated for a −40˚ to +110˚C range (−10˚ with im-
proved accuracy). The LM35 series is available packaged in
hermetic TO-46 transistor packages, while the LM35C,
LM35CA, and LM35D are also available in the plastic TO-92
transistor package. The LM35D is also available in an 8-lead
surface mount small outline package and a plastic TO-220
package.
Features
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Calibrated directly in ˚ Celsius (Centigrade)
Linear + 10.0 mV/˚C scale factor
0.5˚C accuracy guaranteeable (at +25˚C)
Rated for full −55˚ to +150˚C range
Suitable for remote applications
Low cost due to wafer-level trimming
Operates from 4 to 30 volts
Less than 60 µA current drain
Low self-heating, 0.08˚C in still air
Nonlinearity only
±
1
⁄
4
˚C typical
Low impedance output, 0.1
Ω
for 1 mA load
Typical Applications
DS005516-4
DS005516-3
FIGURE 1. Basic Centigrade Temperature Sensor
(+2˚C to +150˚C)
Choose R
1
= −V
S
/50 µA
V
OUT
= +1,500 mV at +150˚C
= +250 mV at +25˚C
= −550 mV at −55˚C
FIGURE 2. Full-Range Centigrade Temperature Sensor
TRI-STATE
®
is a registered trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS005516
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
