LM50
SOT-23Single-Supply Centigrade Temperature Sensor
General Description
The LM50is a precision integrated-circuit temperature sen-sor that can sense a ?40?C to +125?C temperature range us-ing a single positive supply.The LM50’s output voltage is lin-early proportional to Celsius (Centigrade)temperature (+10mV/?C)and has a DC offset of +500mV.The offset al-lows reading negative temperatures without the need for a negative supply.The ideal output voltage of the LM50ranges from +100mV to +1.75V for a ?40?C to +125?C temperature range.The LM50does not require any external calibration or trimming to provide accuracies of ±3?C at room temperature and ±4?C over the full ?40?C to +125?C temperature range.Trimming and calibration of the LM50at the wafer level as-sure low cost and high accuracy.The LM50’s linear output,+500mV offset,and factory calibration simplify circuitry re-quired in a single supply environment where reading nega-tive temperatures is required.Because the LM50’s quiescent current is less than 130μA,self-heating is limited to a very low 0.2?C in still air.
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 +10.0mV/?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 130μA current drain
n Low self-heating,less than 0.2?C in still air n
Nonlinearity less than 0.8?C over temp
Connection Diagram
Order SOT-23Supplied As Number Device Marking
LM50BIM3T5B 1000Units on Tape and Reel
LM50CIM3
T5C 1000Units on Tape and Reel
LM50BIM3X T5B 3000Units on Tape and Reel
LM50CIM3X
T5C
3000Units on Tape and Reel
Typical Application
SOT-23
DS012030-1
Top View
See NS Package Number MA03B
DS012030-3
FIGURE 1.Full-Range Centigrade Temperature Sensor (?40?C to +125?C)
July 1999
LM50SOT-23Single-Supply Centigrade Temperature Sensor
?1999National Semiconductor Corporation https://www.wendangku.net/doc/1a13726101.html,
Absolute Maximum Ratings(Note1)
Supply Voltage+12V to?0.2V Output Voltage(+V S+0.6V)to?1.0V Output Current10mA Storage Temperature?65?C to+150?C Lead Temperature:
SOT Package(Note2):
Vapor Phase(60seconds)215?C Infrared(15seconds)220?C T JMAX,Maximum
Junction Temperature150?C ESD Susceptibility(Note3):
Human Body Model
Machine Model
2000V
250V Operating Ratings(Note1)
Specified Temperature Range:T MIN to T MAX LM50C?40?C to+125?C LM50B?25?C to+100?C Operating Temperature Range?40?C to+150?C θJA(Note4)450?C/W Supply Voltage Range(+V S)+4.5V to+10V
Electrical Characteristics
Unless otherwise noted,these specifications apply for V S=+5V DC and I LOAD=+0.5μA,in the circuit of Figure1.Boldface limits apply for the specified T A=T J=T MIN to T MAX;all other limits T A=T J=+25?C,unless otherwise noted.
Parameter Conditions LM50B LM50C Units
(Limit)
Typical Limit Typical Limit
(Note5)(Note5)
Accuracy T A=+25?C±2.0±3.0?C(max) (Note6)T A=T MAX±3.0±4.0?C(max)
T A=T MIN+3.0,?3.5±4.0?C(max) Nonlinearity(Note7)±0.8±0.8?C(max) Sensor Gain+9.7+9.7mV/?C(min) (Average Slope)+10.3+10.3mV/?C(max) Output Resistance2000400020004000?(max) Line Regulation+4.5V≤V S≤+10V±0.8±0.8mV/V(max) (Note8)±1.2±1.2mV/V(max) Quiescent Current+4.5V≤V S≤+10V130130μA(max) (Note9)180180μA(max) Change of Quiescent+4.5V≤V S≤+10V 2.0 2.0μA(max) Current(Note9)
Temperature Coefficient of+1.0+2.0μA/?C Quiescent Current
Long Term Stability(Note10)T J=125?C,for±0.08±0.08?C
1000hours
Note1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions.
Note2:See AN-450“Surface Mounting Methods and Their Effect on Product Reliability”or the section titled“Surface Mount”found in a current National Semicon-ductor Linear Data Book for other methods of soldering surface mount devices.
Note3:Human body model,100pF discharged through a1.5k?resistor.Machine model,200pF discharged directly into each pin.
Note4:Thermal resistance of the SOT-23package is specified without a heat sink,junction to ambient.
Note5:Limits are guaranteed to National’s AOQL(Average Outgoing Quality Level).
Note6:Accuracy is defined as the error between the output voltage and10mv/?C times the device’s case temperature plus500mV,at specified conditions of volt-age,current,and temperature(expressed in?C).
Note7: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.
Note8: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.
Note9:Quiescent current is defined in the circuit of Figure1.
Note10: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 least46 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 ma-jority of the drift will occur in the first1000hours at elevated temperatures.The drift after1000hours will not continue at the first1000hour rate.
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Typical Performance Characteristics To generate these curves the LM50was mounted to a printed circuit board as shown in Figure2.
Thermal Resistance
Junction to Air
DS012030-21Thermal Time Constant
DS012030-22
Thermal Response in Still Air
with Heat Sink(Figure2)
DS012030-23
Thermal Response
in Stirred Oil Bath
with Heat Sink
DS012030-24Start-Up Voltage
vs Temperature
DS012030-25
Thermal Response in Still
Air without a Heat Sink
DS012030-26
Quiescent Current vs Temperature(Figure1)
DS012030-27Accuracy vs Temperature
DS012030-28
Noise Voltage
DS012030-29
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Typical Performance Characteristics
To generate these curves the LM50was mounted to a printed
circuit board as shown in Figure 2.(Continued)1.0Mounting
The LM50can be applied easily in the same way as other integrated-circuit temperature sensors.It can be glued or ce-mented to a surface and its temperature will be within about 0.2?C of the surface temperature.
This 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 ac-tual temperature of the LM50die would be at an intermediate temperature between the surface temperature and the air temperature.
To ensure good thermal conductivity the backside of the LM50die is directly attached to the GND pin.The lands and traces to the LM50will,of course,be part of the printed cir-cuit board,which is the object whose temperature is being measured.These printed circuit board lands and traces will not cause the LM50s temperature to deviate from the de-sired temperature.
Alternatively,the LM50can 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 LM50and 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 conden-sation can occur.Printed-circuit coatings and varnishes such
as Humiseal and epoxy paints or dips are often used to en-sure that moisture cannot corrode the LM50or its connec-tions.
Temperature Rise of LM50Due to Self-Heating (Thermal Resistance,θJA )
SOT-23SOT-23no heat sink *
small heat fin **
Still air 450?C/W
260?C/W Moving air
180?C/W
*Part soldered to 30gauge wire.
**Heat sink used is 1?2"square printed circuit board with 2oz.foil with part at-
tached as shown in Figure 2.
2.0Capacitive Loads
The LM50handles capacitive loading very well.Without any special precautions,the LM50can drive any capacitive load.The LM50has a nominal 2k ?output impedance (as can be seen in the block diagram).The temperature coefficient of the output resistors is around 1300ppm/?C.Taking into ac-count this temperature coefficient and the initial tolerance of the resistors the output impedance of the LM50will not ex-ceed 4k ?.In an extremely noisy environment it may be nec-essary to add some filtering to minimize noise pickup.It is recommended that 0.1μF be added from V IN to GND to by-
Supply Voltage vs Supply Current
DS012030-30
Start-Up Response
DS012030-31
DS012030-19
FIGURE 2.Printed Circuit Board Used for Heat Sink to Generate All Curves.1?2"Square Printed Circuit Board
with 2oz.Foil or Similar
DS012030-7
FIGURE 3.LM50No Decoupling Required
for Capacitive Load
DS012030-8
FIGURE 4.LM50C with Filter for Noisy Environment https://www.wendangku.net/doc/1a13726101.html,
4
2.0Capacitive Loads
(Continued)
pass the power supply voltage,as shown in Figure 4.In a noisy environment it may be necessary to add a capacitor from the output to ground.A 1μF output capacitor with the 4k ?output impedance will form a 40Hz lowpass filter.Since
the thermal time constant of the LM50is much slower than the 25ms time constant formed by the RC,the overall re-sponse time of the LM50will not be significantly affected.For much larger capacitors this additional time lag will increase the overall response time of the LM50.
3.0Typical Applications
DS012030-17
*R2≈2k with a typical 1300ppm/?C drift.
FIGURE 5.Block Diagram
DS012030-11
FIGURE 6.Centigrade Thermostat/Fan Controller
DS012030-13
FIGURE 7.Temperature To Digital Converter (Serial Output)(+125?C Full Scale)
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3.0Typical Applications(Continued)
DS012030-14
FIGURE8.Temperature To Digital Converter(Parallel TRI-STATE?Outputs for
Standard Data Bus toμP Interface)(125?C Full Scale)
DS012030-16
FIGURE9.LM50With Voltage-To-Frequency Converter And Isolated Output
(?40?C to+125?C;100Hz to1750Hz)
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Physical Dimensions inches(millimeters)unless otherwise noted
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION.As used herein:
1.Life support devices or systems are devices or
systems which,(a)are intended for surgical implant
into the body,or(b)support or sustain life,and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling,can be reasonably expected to result in a
significant injury to the user.
2.A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system,or to affect its
safety or effectiveness.
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SOT-23Molded Small Outline Transistor Package(M3)
Order Number LM50BIM3,or LM50CIM3
NS Package Number MA03B
LM50
SOT-23
Single-Supply
Centigrade
Temperature
Sensor National does not assume any responsibility for use of any circuitry described,no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.