LM135/LM235/LM335, LM135A/LM235A/LM335A
Precision Temperature Sensors
General Description
The LM135 series are precision, easily-calibrated, integrated
circuit temperature sensors. Operating as a 2-terminal zener,
the LM135 has a breakdown voltage directly proportional to
absolute temperature at +10 mV/K. With less than 1
dy-
namic impedance the device operates over a current range
of 400 A to 5 mA with virtually no change in performance.
When calibrated at 25C the LM135 has typically less than
1C error over a 100C temperature range. Unlike other
sensors the LM135 has a linear output.
Applications for the LM135 include almost any type of tem-
perature sensing over a -55C to +150C temperature
range. The low impedance and linear output make interfac-
ing to readout or control circuitry especially easy.
The LM135 operates over a -55C to +150C temperature
range while the LM235 operates over a -40C to +125C
temperature range. The LM335 operates from -40C to
+100C. The LM135/LM235/LM335 are available packaged
in hermetic TO-46 transistor packages while the LM335 is
also available in plastic TO-92 packages.
Features
n
Directly calibrated in Kelvin
n
1C initial accuracy available
n
Operates from 400 A to 5 mA
n
Less than 1
dynamic impedance
n
Easily calibrated
n
Wide operating temperature range
n
200C overrange
n
Low cost
Schematic Diagram
DS005698-1
November 2000
LM135/LM235/LM335,
LM135A/LM235A/LM335A
Precision
T
emperature
Sensors
2000 National Semiconductor Corporation
DS005698
www.national.com
Connection Diagrams
TO-92
Plastic Package
DS005698-8
Bottom View
Order Number LM335Z
or LM335AZ
See NS Package
Number Z03A
SO-8
Surface Mount Package
DS005698-25
Order Number LM335M
See NS Package
Number M08A
TO-46
Metal Can Package*
DS005698-26
*Case is connected to negative pin
Bottom View
Order Number LM135H,
LM135H-MIL, LM235H,
LM335H, LM135AH,
LM235AH or LM335AH
See NS Package
Number H03H
LM135/LM235/LM335,
LM135A/LM235A/LM335A
www.national.com
2
Absolute Maximum Ratings
(Note 4)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Reverse Current
15 mA
Forward Current
10 mA
Storage Temperature
TO-46 Package
-60C to +180C
TO-92 Package
-60C to +150C
SO-8 Package
-65C to +150C
Specified Operating Temp. Range
Continuous
Intermittent
(Note 2)
LM135, LM135A
-55C to +150C
150C to 200C
LM235, LM235A
-40C to +125C
125C to 150C
LM335, LM335A
-40C to +100C
100C to 125C
Lead Temp. (Soldering, 10 seconds)
TO-92 Package:
260C
TO-46 Package:
300C
SO-8 Package:
300C
Vapor Phase (60 seconds):
215C
Infrared (15 seconds):
220C
Temperature Accuracy
(Note 1)
LM135/LM235, LM135A/LM235A
Parameter
Conditions
LM135A/LM235A
LM135/LM235
Units
Min
Typ
Max
Min
Typ
Max
Operating Output Voltage
T
C
= 25C, I
R
= 1 mA
2.97
2.98
2.99
2.95
2.98
3.01
V
Uncalibrated Temperature Error
T
C
= 25C, I
R
= 1 mA
0.5
1
1
3
C
Uncalibrated Temperature Error
T
MIN
T
C
T
MAX
, I
R
= 1 mA
1.3
2.7
2
5
C
Temperature Error with 25C
T
MIN
T
C
T
MAX
, I
R
= 1 mA
0.3
1
0.5
1.5
C
Calibration
Calibrated Error at Extended
T
C
= T
MAX
(Intermittent)
2
2
C
Temperatures
Non-Linearity
I
R
= 1 mA
0.3
0.5
0.3
1
C
Temperature Accuracy
(Note 1)
LM335, LM335A
Parameter
Conditions
LM335A
LM335
Units
Min
Typ
Max
Min
Typ
Max
Operating Output Voltage
T
C
= 25C, I
R
= 1 mA
2.95
2.98
3.01
2.92
2.98
3.04
V
Uncalibrated Temperature Error
T
C
= 25C, I
R
= 1 mA
1
3
2
6
C
Uncalibrated Temperature Error
T
MIN
T
C
T
MAX
, I
R
= 1 mA
2
5
4
9
C
Temperature Error with 25C
T
MIN
T
C
T
MAX
, I
R
= 1 mA
0.5
1
1
2
C
Calibration
Calibrated Error at Extended
T
C
= T
MAX
(Intermittent)
2
2
C
Temperatures
Non-Linearity
I
R
= 1 mA
0.3
1.5
0.3
1.5
C
Electrical Characteristics
(Note 1)
LM135/LM235
LM335
Parameter
Conditions
LM135A/LM235A
LM335A
Units
Min
Typ
Max
Min
Typ
Max
Operating Output Voltage
400 A
I
R
5 mA
2.5
10
3
14
mV
Change with Current
At Constant Temperature
Dynamic Impedance
I
R
=1 mA
0.5
0.6
Output Voltage Temperature
+10
+10
mV/C
Coefficient
Time Constant
Still Air
80
80
sec
100 ft/Min Air
10
10
sec
Stirred Oil
1
1
sec
Time Stability
T
C
=125C
0.2
0.2
C/khr
LM135/LM235/LM335,
LM135A/LM235A/LM335A
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3
Electrical Characteristics
(Note 1) (Continued)
Note 1: Accuracy measurements are made in a well-stirred oil bath. For other conditions, self heating must be considered.
Note 2: Continuous operation at these temperatures for 10,000 hours for H package and 5,000 hours for Z package may decrease life expectancy of the device.
Note 3:
Thermal Resistance
TO-92
TO-46
SO-8
JA
(junction to ambient)
202C/W
400C/W
165C/W
JC
(junction to case)
170C/W
N/A
N/A
Note 4: Refer to RETS135H for military specifications.
Typical Performance Characteristics
Reverse Voltage Change
DS005698-27
Calibrated Error
DS005698-28
Reverse Characteristics
DS005698-29
Response Time
DS005698-30
Dynamic Impedance
DS005698-31
Noise Voltage
DS005698-32
Thermal Resistance
Junction to Air
DS005698-33
Thermal Time Constant
DS005698-34
Thermal Response in Still Air
DS005698-35
LM135/LM235/LM335,
LM135A/LM235A/LM335A
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4
Typical Performance Characteristics
(Continued)
Application Hints
CALIBRATING THE LM135
Included on the LM135 chip is an easy method of calibrating
the device for higher accuracies. A pot connected across the
LM135 with the arm tied to the adjustment terminal allows a
1-point calibration of the sensor that corrects for inaccuracy
over the full temperature range.
This single point calibration works because the output of the
LM135 is proportional to absolute temperature with the ex-
trapolated output of sensor going to 0V output at 0K
(-273.15C). Errors in output voltage versus temperature are
only slope (or scale factor) errors so a slope calibration at
one temperature corrects at all temperatures.
The output of the device (calibrated or uncalibrated) can be
expressed as:
where T is the unknown temperature and T
o
is a reference
temperature, both expressed in degrees Kelvin. By calibrat-
ing the output to read correctly at one temperature the output
at all temperatures is correct. Nominally the output is cali-
brated at 10 mV/K.
To insure good sensing accuracy several precautions must
be taken. Like any temperature sensing device, self heating
can reduce accuracy. The LM135 should be operated at the
lowest current suitable for the application. Sufficient current,
of course, must be available to drive both the sensor and the
calibration pot at the maximum operating temperature as
well as any external loads.
If the sensor is used in an ambient where the thermal resis-
tance is constant, self heating errors can be calibrated out.
This is possible if the device is run with a temperature stable
current. Heating will then be proportional to zener voltage
and therefore temperature. This makes the self heating error
proportional to absolute temperature the same as scale
factor errors.
WATERPROOFING SENSORS
Meltable inner core heat shrinkable tubing such as manufac-
tured by Raychem can be used to make low-cost waterproof
sensors. The LM335 is inserted into the tubing about
1
/
2
"
from the end and the tubing heated above the melting point
of the core. The unfilled
1
/
2
" end melts and provides a seal
over the device.
Typical Applications
Thermal Response in Stirred Oil Bath
DS005698-36
Forward Characteristics
DS005698-37
Basic Temperature Sensor
DS005698-2
Calibrated Sensor
DS005698-9
*Calibrate for 2.982V at 25C
Wide Operating Supply
DS005698-10
LM135/LM235/LM335,
LM135A/LM235A/LM335A
www.national.com
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