LM50C MDC - National Semiconductor

TL/H/12030

LM50B/LM50C SOT-23 Single-Supply Centigrade Temperature Sensor

June 1996

LM50B/LM50C

SOT-23 Single-Supply Centigrade Temperature Sensor

General Description

The LM50 is a precision integrated-circuit temperature sen-

sor that can sense a b40§Ctoa

125§C temperature range

using a single positive supply. The LM50’s output voltage is

linearly proportional to Celsius (Centigrade) temperature

(a10 mV/§C) and has a DC offset of a500 mV. The offset

allows reading negative temperatures without the need for a

negative supply. The ideal output voltage of the LM50

ranges from a100 mV to a1.75V for a b40§Ctoa

125§C

temperature range. The LM50 does not require any external

calibration or trimming to provide accuracies of g3§Cat

room temperature and g4§C over the full b40§Cto

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, a500 mV offset, and factory cali-

bration simplify circuitry required in a single supply environ-

ment where reading negative temperatures is required. Be-

cause the LM50’s quiescent current is less than 130 mA,

self-heating is limited to a very low 0.2§C in still air.

Applications

YComputers

YDisk Drives

YBattery Management

YAutomotive

YFAX Machines

YPrinters

YPortable Medical Instruments

YHVAC

YPower Supply Modules

Features

YCalibrated directly in §Celsius (Centigrade)

YLinear a10.0 mV/§C scale factor

Yg2§C accuracy guaranteed at a25§C

YSpecified for full b40§to a125§C range

YSuitable for remote applications

YLow cost due to wafer-level trimming

YOperates from 4.5V to 10V

YLess than 130 mA current drain

YLow self-heating, less than 0.2§C in still air

YNonlinearity less than 0.8§C over temp

Connection Diagram

SOT-23

TL/H/12030–1

Top View

See NS Package Number M03B

(JEDEC Registration TO-236AB)

Order SOT-23 Supplied As

Number Device Marking

LM50BIM3 T5B 250 Units on Tape and Reel

LM50CIM3 T5C 250 Units on Tape and Reel

LM50BIM3X T5B 3000 Units on Tape and Reel

LM50CIM3X T5C 3000 Units on Tape and Reel

Typical Application

TL/H/12030–3

FIGURE 1. Full-Range Centigrade Temperature Sensor (b40§Ctoa

125§C)

C1996 National Semiconductor Corporation RRD-B30M76/Printed in U. S. A. http://www.national.com

Absolute Maximum Ratings (Note 1)

Supply Voltage a12V to b0.2V

Output Voltage (aVSa0.6V) to b1.0V

Output Current 10 mA

Storage Temperature b65§Ctoa

150§C

Lead Temperature

SOT Package (Note 2):

Vapor Phase (60 seconds) 215§C

Infrared (15 seconds) 220§C

TJMAX, Maximum Junction Temperature 150§C

ESD Susceptibility (Note 3):

Human Body Model 2000V

Machine Model 200V

Operating Ratings (Note 1)

Specified Temperature Range: TMIN to TMAX

LM50C b40§Ctoa

125§C

LM50B b25§Ctoa

100§C

Operating Temperature Range b40§Ctoa

150§C

iJA (Note 4) 450§C/W

Supply Voltage Range (aVS)a4.5V to a10V

Electrical Characteristics Unless otherwise noted, these specifications apply for VSea

DC and ILOAD e

a0.5 mA, in the circuit of

Figure 1.

Boldface limits apply for the specified TAeTJeTMIN to TMAX; all other limits TA

eTJea

25§C, unless otherwise noted.

Parameter Conditions

LM50B LM50C

(Limit)

Units

Typical Limit Typical Limit

(Note 5) (Note 5)

Accuracy TAea

25§Cg2.0 g3.0 §C (max)

(Note 6) TAeTMAX g3.0 g4.0 §C (max)

TAeTMIN a3.0, b3.5 g4.0 §C (max)

Nonlinearity (Note 7) g0.8 g0.8 §C (max)

Sensor Gain a9.7 a9.7 mV/§C (min)

(Average Slope) a10.3 a10.3 mV/§C (max)

Output Resistance 2000 4000 2000 4000 X(max)

Line Regulation a4.5V sVSsa10V g0.8 g0.8 mV/V (max)

(Note 8) g1.2 g1.2 mV/V (max)

Quiescent Current a4.5V sVSsa10V 130 130 mA (max)

(Note 9) 180 180 mA (max)

Change of Quiescent a4.5V sVSsa10V 2.0 2.0 mA (max)

Current (Note 8)

Temperature Coefficient of a1.0 a2.0 mA/§C

Quiescent Current

Long Term Stability (Note 10) TJe125§C, for g0.08 g0.08 §C

1000 hours

Note 1: 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.

Note 2: See AN-450 ‘‘Surface Mounting Methods and Their Effect on Product Reliability’’ or the 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 kXresistor. 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 the error between the output voltage and 10mv/§C times the device’s case temperature, at specified conditions of voltage, 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

computed by multiplying the internal dissipation by the thermal resistance.

Note 9: Quiescent current is defined in the circuit of

Figure 1

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.

http://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

Junction to Air

Thermal Resistance

Thermal Time Constant with Heat Sink (

Figure 2

)

Thermal Response in Still Air

with Heat Sink

in Stirred Oil Bath

Thermal Response

vs Temperature

Start-Up Voltage

Air without a Heat Sink

Thermal Response in Still

Temperature

(Figure 1)

Quiescent Current vs

Accuracy vs Temperature Noise Voltage

vs Supply Current

Supply Voltage

Start-Up Response

TL/H/12030–19

FIGURE 2. Printed Circuit Board Used

for Heat Sink to Generate All Curves.

(/2×Square Printed Circuit Board

with 2 oz. Foil or Similar

TL/H/12030–18

http://www.national.com3

1.0 Mounting

The LM50 can be applied easily in the same way as other

integrated-circuit temperature sensors. It can be glued or

cemented 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 actual temperature of the LM50 die would be at an inter-

mediate temperature between the surface temperature and

the air temperature.

To ensure good thermal conductivity the backside of the

LM50 die is directly attached to the GND pin. The lands and

traces to the LM50 will, of course, be part of the printed

circuit board, which is the object whose temperature is be-

ing measured. These printed circuit board lands and traces

will not cause the LM50s temperature to deviate from the

desired temperature.

Alternatively, the LM50 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 LM50 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 var-

nishes such as Humiseal and epoxy paints or dips are often

used to ensure that moisture cannot corrode the LM50 or its

connections.

Temperature Rise of LM50 Due to Self-Heating

(Thermal Resistance, iJA)

SOT-23** SOT-23

no heat sink small heat fin*

Still air 450§C/W 260§C/W

Moving air 180§C/W

*Heat sink used is (/2×square printed circuit board with 2 oz. foil with part

attached as shown in

Figure 2

** Part soldered to 30 gauge wire.

2.0 Capacitive Loads

TL/H/12030–7

FIGURE 3. LM50 No Decoupling Required

for Capacitive Load

TL/H/12030–8

FIGURE 4. LM50C with Filter for Noisy Environment

The LM50 handles capacitive loading very well. Without any

special precautions, the LM50 can drive any capacitive load.

The LM50 has a nominal 2 kXoutput impedance (as can be

seen in the block diagram). The temperature coefficient of

the output resistors is around 1300 ppm/§C. Taking into ac-

count this temperature coefficient and the initial tolerance of

the resistors the output impedance of the LM50 will not ex-

ceed 4 kX. In an extremely noisy environment it may be

necessary to add some filtering to minimize noise pickup. It

is recommended that 0.1 mF be added from VIN to GND to

bypass the power supply voltage, as shown in

Figure 4

.Ina

noisy environment it may be necessary to add a capacitor

from the output to ground. A 1 mF output capacitor with the

4kXoutput impedance will form a 40 Hz lowpass filter.

Since the thermal time constant of the LM50 is much slower

than the 25 ms time constant formed by the RC, the overall

response time of the LM50 will not be significantly affected.

For much larger capacitors this additional time lag will in-

crease the overall response time of the LM50.

TL/H/12030–17

*R2 &2k with a typical 1300 ppm/§C drift.

FIGURE 5. Block Diagram

http://www.national.com 4

3.0 Typical Applications

TL/H/12030–11

FIGURE 6. Centigrade Thermostat/Fan Controller

TL/H/12030–13

FIGURE 7. Temperature To Digital Converter (Serial Output) (a125§C Full Scale)

TL/H/12030–14

FIGURE 8. Temperature To Digital Converter (Parallel TRI-STATEÉOutputs for

Standard Data Bus to mP Interface) (125§C Full Scale)

http://www.national.com5

3.0 Typical Applications (Continued)

TL/H/12030–16

FIGURE 9. LM50 With Voltage-To-Frequency Converter And Isolated Output

(b40§Ctoa

125§C; 100 Hz to 1750 Hz)

4.0 Recommended Solder Pads for SOT-23 Package

SOT-23

TL/H/12030–20

http://www.national.com 6

http://www.national.com7

LM50B/LM50C SOT-23 Single-Supply Centigrade Temperature Sensor

Physical Dimensions inches (millimeters) unless otherwise noted

SOT-23 Molded Small Outline Transistor Package (M3)

Order Number LM50BIM3, or LM50CIM3

NS Package Number M03B

(JEDEC Registration TO-236AB)

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 OF NATIONAL

SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or 2. A critical component is any component of a life

systems which, (a) are intended for surgical implant support device or system whose failure to perform can

into the body, or (b) support or sustain life, and whose be reasonably expected to cause the failure of the life

failure to perform, when properly used in accordance support device or system, or to affect its safety or

with instructions for use provided in the labeling, can effectiveness.

be reasonably expected to result in a significant injury

to the user.

National Semiconductor National Semiconductor National Semiconductor National Semiconductor

Corporation Europe Hong Kong Ltd. Japan Ltd.

1111 West Bardin Road Fax:

49 (0) 180-530 85 86 13th Floor, Straight Block, Tel: 81-043-299-2308

Arlington, TX 76017 Email: europe.support

nsc.com Ocean Centre, 5 Canton Rd. Fax: 81-043-299-2408

Tel: 1(800) 272-9959 Deutsch Tel:

49 (0) 180-530 85 85 Tsimshatsui, Kowloon

Fax: 1(800) 737-7018 English Tel:

49 (0) 180-532 78 32 Hong Kong

Fran3ais Tel:

49 (0) 180-532 93 58 Tel: (852) 2737-1600

http://www.national.com

Italiano Tel:

49 (0) 180-534 16 80 Fax: (852) 2736-9960

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.