Rainbow Electronics LM50 User Manual
July 1999
LM50
SOT-23 Single-Supply Centigrade Temperature Sensor
LM50 SOT-23 Single-Supply Centigrade Temperature Sensor
General Description
The LM50 is a precision integrated-circuit temperature sensor thatcan sense a −40˚C to +125˚C temperature range using asingle positive supply. The LM50’s outputvoltage is linearly proportional to Celsius (Centigrade) temperature
(+10 mV/˚C) and has a DC offset of +500 mV. The offset allows reading negative temperatures without the need for a
negative supply. The idealoutput voltageof theLM50 ranges
from +100 mV to +1.75V for a −40˚C to +125˚C temperature
range. The LM50 does not requireany externalcalibration or
trimming toprovide accuracies of
±
and
4˚C over the full −40˚C to +125˚C temperature range.
Trimming and calibration of the LM50 at the wafer level assure low cost and high accuracy. The LM50’s linear output,
+500 mV offset, and factory calibration simplify circuitry required in a single supply environment where reading negative temperatures is required. Because the LM50’squiescent
current is less than 130 µA, self-heating is limited to a very
low 0.2˚C in still air.
±
3˚C atroom temperature
Connection Diagram
SOT-23
DS012030-1
See NS Package Number MA03B
Top View
Applications
n Computers
n Disk Drives
n Battery Management
n Automotive
n FAX Machines
n Printers
n Portable Medical Instruments
n HVAC
n Power Supply Modules
Features
n Calibrated directly in degree Celsius (Centigrade)
n Linear + 10.0 mV/˚C scale factor
±
n
2˚C accuracy guaranteed at +25˚C
n Specified for full −40˚ to +125˚C range
n Suitable for remote applications
n Low cost due to wafer-level trimming
n Operates from 4.5V to 10V
n Less than 130 µA current drain
n Low self-heating, less than 0.2˚C in still air
n Nonlinearity less than 0.8˚C over temp
Order SOT-23 Supplied As
Number Device Marking
LM50BIM3 T5B 1000 Units on Tape
LM50CIM3 T5C 1000 Units on Tape
LM50BIM3X T5B 3000 Units on Tape
LM50CIM3X T5C 3000 Units on Tape
and Reel
and Reel
and Reel
and Reel
Typical Application
DS012030-3
FIGURE 1. Full-Range Centigrade Temperature Sensor (−40˚C to +125˚C)
© 1999 National Semiconductor Corporation DS012030 www.national.com
Absolute Maximum Ratings (Note 1)
Supply Voltage +12V to −0.2V
Output Voltage (+V
Output Current 10 mA
Storage Temperature −65˚C to +150˚C
Lead Temperature:
SOT Package (Note 2):
Vapor Phase (60 seconds) 215˚C
Infrared (15 seconds) 220˚C
, Maximum
T
JMAX
Junction Temperature 150˚C
+ 0.6V) to −1.0V
S
ESD Susceptibility (Note 3):
Human Body Model
Machine Model
2000V
250V
Operating Ratings (Note 1)
Specified Temperature Range: T
LM50C −40˚C to +125˚C
LM50B −25˚C to +100˚C
Operating Temperature Range −40˚C to +150˚C
(Note 4) 450˚C/W
θ
JA
Supply Voltage Range (+V
) +4.5V to +10V
S
MIN
to T
MAX
Electrical Characteristics
Unless otherwise noted, these specifications apply for V
limits apply for the specified T
=
=
T
A
to T
T
J
MIN
=
+5 V
S
; all other limits T
MAX
and I
DC
Parameter Conditions LM50B LM50C Units
Typical Limit Typical Limit
=
Accuracy T
(Note 6) T
+25˚C
A
=
T
A
MAX
=
T
T
A
MIN
Nonlinearity (Note 7)
Sensor Gain +9.7 +9.7 mV/˚C (min)
(Average Slope) +10.3 +10.3 mV/˚C (max)
Output Resistance 2000 4000 2000 4000 Ω (max)
Line Regulation +4.5V ≤ V
≤ +10V
S
(Note 8)
Quiescent Current +4.5V ≤ V
≤ +10V 130 130 µA (max)
S
(Note 9) 180 180 µA (max)
Change of Quiescent +4.5V ≤ V
≤ +10V 2.0 2.0 µA (max)
S
Current (Note 9)
Temperature Coefficient of +1.0 +2.0 µA/˚C
Quiescent Current
Long Term Stability (Note 10) T
=
J
125˚C, for
±
0.08
1000 hours
Note 1: Absolute Maximum Ratingsindicate limits beyondwhich damage tothe device may occur. DC andACelectrical specifications do not apply when operating
the device beyond its rated operating conditions.
Note 2: See AN-450 “SurfaceMounting Methods and Their Effect on Product Reliability” orthe section titled “Surface Mount” found in a current National Semiconductor Linear Data Book for other methods of soldering surface mount devices.
Note 3: Human body model, 100 pF discharged through a 1.5 kΩ resistor. Machine model, 200 pF discharged directly into each pin.
Note 4: Thermal resistance of the SOT-23 package is specified without a heat sink, junction to ambient.
Note 5: Limits are guaranteed to National’s AOQL(Average Outgoing Quality Level).
Note 6: Accuracy is defined as theerror between the output voltageand 10mv/˚C times the device’s case temperatureplus 500 mV, atspecified conditions of volt-
age, current, and temperature (expressed in ˚C).
Note 7: Nonlinearity is defined as the deviation of the output-voltage-versus-temperature curve from the best-fit straight line, over the device’s rated temperature
range.
Note 8: Regulation is measured at constant junction temperature, using pulse testing with a low duty cycle. Changes in output due to heating effects can be com-
puted by multiplying the internal dissipation by the thermal resistance.
Note 9: Quiescent current is defined in the circuit of
Note 10: For best long-term stability, any precision circuit will give best results if the unit is aged at a warm temperature, and/or temperature cycled for at least 46
hours before long-term life test begins. This is especially true when a small (Surface-Mount)part is wave-soldered;allow time for stress relaxation to occur. The majority of the drift will occur in the first 1000 hours at elevated temperatures. The drift after 1000 hours will not continue at the first 1000 hour rate.
Figure 1
.
=
+0.5 µA, in the circuit of
LOAD
=
=
T
+25˚C, unless otherwise noted.
A
J
(Note 5) (Note 5)
±
2.0
±
3.0
+3.0, −3.5
±
0.8
±
0.8
±
1.2
±
0.08 ˚C
±
±
±
±
±
±
Figure 1
. Boldface
(Limit)
3.0 ˚C (max)
4.0 ˚C (max)
4.0 ˚C (max)
0.8 ˚C (max)
0.8 mV/V (max)
1.2 mV/V (max)
www.national.com 2
Typical Performance Characteristics To generate these curves the LM50 was mounted to a printed
circuit board as shown in
Figure 2
.
Thermal Resistance
Junction to Air
Thermal Response
in Stirred Oil Bath
with Heat Sink
Quiescent Current vs
Temperature (
Figure 1
)
DS012030-21
DS012030-24
Thermal Time Constant
Start-Up Voltage
vs Temperature
Accuracy vs Temperature
DS012030-22
DS012030-25
Thermal Response in Still Air
with Heat Sink (
Figure 2
)
DS012030-23
Thermal Response in Still
Air without a Heat Sink
DS012030-26
Noise Voltage
DS012030-27
DS012030-28
DS012030-29
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