LM26CIM5X-DPB/NOPB - NATIONAL SEMICONDUCTOR

July 31, 2008

LM26

SOT-23, ±3°C Accurate, Factory Preset Thermostat

General Description

The LM26 is a precision, single digital-output, low-power ther-

mostat comprised of an internal reference, DAC, temperature

sensor and comparator. Utilizing factory programming, it can

be manufactured with different trip points as well as different

digital output functionality. The trip point (TOS) can be preset

at the factory to any temperature in the range of −55°C to

+110°C in 1°C increments. The LM26 has one digital output

(OS/OS/US/US), one digital input (HYST) and one analog

output (VTEMP). The digital output stage can be preset as ei-

ther open-drain or push-pull. In addition, it can be factory

programmed to be active HIGH or LOW. The digital output

can be factory programmed to indicate an over temperature

shutdown event (OS or OS) or an under temperature shut-

down event (US or US). When preset as an overtemperature

shutdown (OS) it will go LOW to indicate that the die temper-

ature is over the internally preset TOS and go HIGH when the

temperature goes below (TOS–THYST). Similarly, when pre-

programmed as an undertemperature shutdown (US) it will

go HIGH to indicate that the temperature is below TUS and go

LOW when the temperature is above (TUS+THYST). The typical

hysteresis, THYST, can be set to 2°C or 10°C and is controlled

by the state of the HYST pin. A VTEMP analog output provides

a voltage that is proportional to temperature and has a

−10.82mV/°C output slope.

Available parts are detailed in the ordering information. For

other part options, contact a National Semiconductor Distrib-

utor or Sales Representative for information on minimum

order qualification. The LM26 is currently available in a 5-lead

SOT-23 package.

Applications

■Microprocessor Thermal Management

■Appliances

■Portable Battery Powered Systems

■Fan Control

■Industrial Process Control

■HVAC Systems

■Remote Temperature Sensing

■Electronic System Protection

Features

■Internal comparator with pin programmable 2°C or 10°C

hysteresis

■No external components required

■Open Drain or push-pull digital output; supports CMOS

logic levels

■Internal temperature sensor with VTEMP output pin

■VTEMP output allows after-assembly system testing

■Internal voltage reference and DAC for trip-point setting

■Currently available in 5-pin SOT-23 plastic package

■Excellent power supply noise rejection

■UL Recognized Component

Key Specifications

■ Power Supply Voltage 2.7V to 5.5V

■ Power Supply Current 40µA(max)

20µA(typ)

■ Hysteresis Temperature 2°C or 10°C(typ)

Temperature Trip Point Accuracy

Temperature Range LM26CIM

−55°C to +110°C ±3°C (max)

+120°C ±4°C (max)

LM26CIM5-TPA Simplified Block Diagram and Connection Diagram

10132301

The LM26CIM5-TPA has a fixed trip point of 85°C.

For other trip point and output function availability,

please see ordering information or contact National Semiconductor.

LM26 SOT-23, ±3°C Accurate, Factory Preset Thermostat

Ordering Information

For more detailed information on the suffix meaning see the part number template at the end of the Electrical Characteristics

Section. Contact National Semiconductor for other set points and output options.

Order Number

Top Mark

NS Package

Number

Trip Point Setting Output Function

Bulk Rail 3000 Units in Tape &

Reel

LM26CIM5-DPB LM26CIM5X-DPB TDPB MA05B −25°C Open Drain US

LM26CIM5-HHD LM26CIM5X-HHD THHD MA05B 0°C Push Pull US

LM26CIM5-NPA LM26CIM5X-NPA TNPA MA05B 45°C Open Drain OS

LM26CIM5-PHA LM26CIM5X-PHA TPHA MA05B 50°C Open Drain OS

LM26CIM5-RPA LM26CIM5X-RPA TRPA MA05B 65°C Open Drain OS

LM26CIM5-SHA LM26CIM5X-SHA TSHA MA05B 70°C Open Drain OS

LM26CIM5-SPA LM26CIM5X-SPA TSPA MA05B 75°C Open Drain OS

LM26CIM5-TPA LM26CIM5X-TPA TTPA MA05B 85°C Open Drain OS

LM26CIM5-VHA LM26CIM5X-VHA TVHA MA05B 90°C Open Drain OS

LM26CIM5-VPA LM26CIM5X-VPA TVPA MA05B 95°C Open Drain OS

LM26CIM5-XHA LM26CIM5X-XHA TXHA MA05B 100°C Open Drain OS

LM26CIM5-XPA LM26CIM5X-XPA TXPA MA05B 105°C Open Drain OS

LM26CIM5-YHA LM26CIM5X-YHA TYHA MA05B 110°C Open Drain OS

LM26CIM5-YPA LM26CIM5X-YPA TYPA MA05B 115°C Open Drain OS

LM26CIM5-ZHA LM26CIM5X-ZHA TZHA MA05B 120°C Open Drain OS

Connection Diagram

10132302

Pin Descriptions

Number

Name

Function Connection

1 HYST Hysteresis control, digital input GND for 10°C or V+ for 2°C

2 GND Ground, connected to the back side of the die

through lead frame.

System GND

3 VTEMP Analog output voltage proportional to

temperature

Leave floating or connect to a high impedance node.

4 V+Supply input 2.7V to 5.5V with a 0.1µF bypass capacitor. For PSRR

information see Section Titled NOISE CONSIDERATIONS.

5 OS Overtemperature Shutdown open-drain active

low thermostat digital output

Controller interrupt, system or power supply shutdown; pull-up

resistor ≥ 10kΩ

OS Overtemperature Shutdown push-pull active

high thermostat digital output

Controller interrupt, system or power supply shutdown

US Undertemperature Shutdown open-drain active

low thermostat digital output

System or power supply shutdown; pull-up resistor ≥ 10kΩ

US Undertemperature Shutdown push-pull active

high thermostat digital output

System or power supply shutdown

Note: pin 5 functionality and trip point setting are programmed during LM26 manufacture.

www.national.com 2

LM26

Absolute Maximum Ratings (Note 1)

Input Voltage 6.0V

Input Current at any pin (Note 2) 5mA

Package Input Current(Note 2) 20mA

Package Dissipation at TA = 25°C

(Note 3) 500mW

Soldering Information

SOT23 Package

Vapor Phase (60 seconds)

Infrared (15 seconds)

215°C

220°C

Storage Temperature −65°C to + 150°C

ESD Susceptibility (Note 4)

Human Body Model

Machine Model

2500V

250V

Operating Ratings (Note 1)

Specified Temperature Range TMIN ≤ TA ≤ TMAX

LM26CIM −55°C ≤ TA ≤ +125°C

Positive Supply Voltage (V+)+2.7V to +5.5V

Maximum VOUT +5.5V

LM26 Electrical Characteristics

The following specifications apply for V+ = 2.7VDC to 5.5VDC, and VTEMP load current = 0µA unless otherwise specified. Boldface

limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25°C unless otherwise specified.

Typical LM26CIM Units

Symbol Parameter Conditions (Note 6) Limits (Limits)

(Note 7)

Temperature Sensor

Trip Point Accuracy (Includes VREF, DAC,

Comparator Offset, and Temperature

Sensitivity errors)

-55°C ≤ TA ≤ +110°C ±3 °C (max)

+120°C ±4 °C (max)

Trip Point Hysteresis HYST = GND 11 °C

HYST = V+2 °C

VTEMP Output Temperature Sensitivity −10.82 mV/°C

VTEMP Temperature Sensitivity Error to

Equation:

VO = (−3.479×10−6×(T−30)2)

+ (−1.082×10−2×(T−30)) + 1.8015V

−30°C ≤ TA ≤ 120°C,

2.7V ≤ V+ ≤ 5.5V

±3 °C (max)

−55°C ≤ TA ≤ 120°C,

4.5V ≤ V+ ≤ 5.5V

±3 °C (max)

TA = 30°C ±2.5 °C (max)

VTEMP Load Regulation Source ≤ 1 μA0.070 mV

Sink ≤ 40 μA 0.7 mV (max)

VTEMP Line Regulation +2.7V ≤ V+ ≤ +5.5V,

−30°C ≤ TA ≤ +120°C

−0.2 mV/V

ISSupply Current 16 20

µA (max)

Digital Output and Input

IOUT(“1”) Logical “1” Output Leakage Current

(Note 9)

V+ = +5.0V 0.001 1 µA (max)

VOUT(“0”) Logical “0” Output Voltage IOUT = +1.2mA and

V+≥2.7V; IOUT = +3.2mA

and V+≥4.5V; (Note 8)

0.4 V (max)

VOUT(“1”) Logical “1” Push-Pull Output Voltage ISOURCE = 500µA, V+ ≥

2.7V

0.8 × V+V (min)

ISOURCE = 800µA, V

+≥4.5V

V+ − 1.5 V (min)

VIH HYST Input Logical ”1“ Threshold

Voltage

0.8 × V+V (min)

VIL HYST Input Logical ”0“ Threshold

Voltage

0.2 × V+V (max)

3 www.national.com

LM26

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is

functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed

specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test

conditions.

Note 2: When the input voltage (VI) at any pin exceeds the power supply (VI < GND or VI > V+), the current at that pin should be limited to 5mA. The 20mA

maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5mA to four. Under normal

operating conditions the maximum current that pins 2, 4 or 5 can handle is limited to 5mA each.

Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax (maximum junction temperature), θJA (junction to

ambient thermal resistance) and TA (ambient temperature). The maximum allowable power dissipation at any temperature is PD = (TJmax–TA)/θJA or the number

given in the Absolute Maximum Ratings, whichever is lower. For this device, TJmax = 150°C. For this device the typical thermal resistance (θJA) of the different

package types when board mounted follow:

Package Type θJA

SOT23-5, MA05B 250°C/W

Note 4: The human body model is a 100pF capacitor discharge through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged

directly into each pin.

Note 5: See the URL ”http://www.national.com/packaging/“ for other recommendations and methods of soldering surface mount devices.

Note 6: Typicals are at TJ = TA = 25°C and represent most likely parametric norm.

Note 7: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).

Note 8: Care should be taken to include the effects of self heating when setting the maximum output load current. The power dissipation of the LM26 would

increase by 1.28mW when IOUT=3.2mA and VOUT=0.4V. With a thermal resistance of 250°C/W, this power dissipation would cause an increase in the die

temperature of about 0.32°C due to self heating. Self heating is not included in the trip point accuracy specification.

Note 9: The 1µA limit is based on a testing limitation and does not reflect the actual performance of the part. Expect to see a doubling of the current for every

15°C increase in temperature. For example, the 1nA typical current at 25°C would increase to 16nA at 85°C.

Part Number Template

The series of digits labeled xyz in the part number LM26CIM-xyz, describe the set point value and the function of the output as

follows:

The place holders xy describe the set point temperature as shown in the following table.

x (10x) y (1x) Temperature (°C)

A - −5

B - −4

C - −3

D - −2

E - −1

F - −0

H H 0

J J 1

K K 2

L L 3

x (10x) y (1x) Temperature (°C)

N N 4

P P 5

R R 6

S S 7

T T 8

V V 9

X - 10

Y - 11

Z - 12

The value of z describes the assignment/function of the output as shown in the following table:

Active-Low/High Open-Drain/ Push-

Pull OS/US Value of z Digital Output Function

0 0 0 A Active-Low, Open-Drain, OS output

0 0 1 B Active-Low, Open-Drain, US output

1 1 0 C Active-High, Push-Pull, OS output

1 1 1 D Active-High, Push-Pull, US output

For example:

•the part number LM26CIM5-TPA has TOS = 85°C, and programmed as an active-low open-drain overtemperature shutdown

output.

•the part number LM26CIM5-FPD has TUS = −5°C, and programmed as an active-high, push-pull undertemperature shutdown

output.

Active-high open-drain and active-low push-pull options are available, please contact National Semiconductor for more information.

www.national.com 4

LM26

Functional Description

LM26 OPTIONS

10132312

LM26-_ _A

10132313

LM26-_ _B

10132314

LM26-_ _C

10132315

LM26-_ _D

FIGURE 1. Output Pin Options Block Diagrams

The LM26 can be factory programmed to have a trip point

anywhere in the range of −55°C to +110°C.

Applications Hints

AFTER-ASSEMBLY PCB TESTING

The LM26's VTEMP output allows after-assembly PCB testing

by following a simple test procedure. Simply measuring the

VTEMP output voltage will verify that the LM26 has been as-

sembled properly and that its temperature sensing circuitry is

functional. The VTEMP output has very weak drive capability

that can be overdriven by 1.5mA. Therefore, one can simply

force the VTEMP voltage to cause the digital output to change

state, thereby verifying that the comparator and output cir-

cuitry function after assembly. Here is a sample test proce-

dure that can be used to test the LM26CIM5-TPA which has

an 85°C trip point.

1. Turn on V+ and measure VTEMP. Then calculate the

temperature reading of the LM26 using the equation:

VO = (−3.479×10−6×(T−30)2) + (−1.082×10−2×(T

−30)) + 1.8015V (1)

(2)

2. Verify that the temperature measured in step one is

within (±3°C + error of reference temperature sensor) of

the ambient/board temperature. The ambient/board

temperature (reference temperature) should be

measured using an extremely accurate calibrated

temperature sensor.

A. Observe that OS is high.

B. Drive VTEMP to ground.

C. Observe that OS is now low.

D. Release the VTEMP pin.

E. Observe that OS is now high.

A. Observe that OS is high.

B. Drive VTEMP voltage down gradually.

C. When OS goes low, note the VTEMP voltage.

D. VTEMPTrig = VTEMP at OS trigger (HIGH->LOW)

E. Calculate Ttrig using Equation 2.

A. Gradually raise VTEMP until OS goes HIGH. Note

VTEMP.

B. Calculate THYST using Equation 2.

VTEMP LOADING

The VTEMP output has very weak drive capability (1 µA source,

40 µA sink). So care should be taken when attaching circuitry

to this pin. Capacitive loading may cause the VTEMP output to

oscillate. Simply adding a resistor in series as shown in Figure

2 will prevent oscillations from occurring. To determine the

value of the resistor follow the guidelines given in Table 1. The

same value resistor will work for either placement of the re-

sistor. If an additional capacitive load is placed directly on the

LM26 output, rather than across CLOAD, it should be at least

a factor of 10 smaller than CLOAD.

5 www.national.com

LM26

TABLE 1. Resistive compensation for capacitive loading

of VTEMP

CLOAD R (Ω)

≤100pF 0

1nF 8200

10nF 3000

100nF 1000

≥1µF 430

10132317

a) R in series with capacitor

10132318

b) R in series with signal path

FIGURE 2. Resistor placement for capacitive loading

compensation of VTEMP

NOISE CONSIDERATIONS

The LM26 has excellent power supply noise rejection. Listed

below is a variety of signals used to test the LM26 power sup-

ply rejection. False triggering of the output was not observed

when these signals where coupled into the V+ pin of the

LM26.

•square wave 400kHz, 1Vp-p

•square wave 2kHz, 200mVp-p

•sine wave 100Hz to 1MHz, 200mVp-p

Testing was done while maintaining the temperature of the

LM26 one degree centigrade way from the trip point with the

output not activated.

MOUNTING CONSIDERATIONS

The LM26 can be applied easily in the same way as other

integrated-circuit temperature sensors. It can be glued or ce-

mented to a surface. The temperature that the LM26 is sens-

ing will be within about +0.06°C of the surface temperature to

which the LM26's leads are attached to.

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 measured would be at an intermediate temper-

ature between the surface temperature and the air tempera-

ture.

To ensure good thermal conductivity, the backside of the

LM26 die is directly attached to the GND pin (pin 2). The tem-

peratures of the lands and traces to the other leads of the

LM26 will also affect the temperature that is being sensed.

Alternatively, the LM26 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 LM26 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 conden-

sation can occur. Printed-circuit coatings and varnishes such

as Humiseal and epoxy paints or dips are often used to ensure

that moisture cannot corrode the LM26 or its connections.

The junction to ambient thermal resistance (θJA) is the pa-

rameter used to calculate the rise of a part's junction temper-

ature due to its power dissipation. For the LM26 the equation

used to calculate the rise in the die junction temperature is as

follows:

(3)

where TA is the ambient temperature, V+ is the power supply

voltage, IQ is the quiescent current, IL_TEMP is the load current

on the VTEMP output, VDO is the voltage on the digital output,

and IDO is the load current on the digital output. Since the

LM26's junction temperature is the actual temperature being

measured, care should be taken to minimize the load current

that the LM26 is required to drive.

The tables shown in Figure 3 summarize the thermal resis-

tance for different conditions and the rise in die temperature

of the LM26 without any loading on VTEMP and a 10k pull-up

resistor on an open-drain digital output with a 5.5V power

supply.

SOT23-5

no heat sink

SOT23-5

small heat sink

θJA

(°C/W)

TJ−TA

(°C)

θJA

(°C/W)

TJ−TA

(°C)

Still Air 250 0.11 TBD TBD

Moving Air TBD TBD TBD TBD

FIGURE 3. Thermal resistance (θJA) and temperature rise

due to self heating (TJ−TA)

www.national.com 6

LM26

Typical Applications

10132303

Note: The fan's control pin has internal pull-up. The 10k pull-down sets a slow fan speed. When the output of the LM26 goes low, the fan will speed up.

FIGURE 4. Two Speed Fan Speed Control

10132320

FIGURE 5. Fan High Side Drive

10132321

FIGURE 6. Fan Low Side Drive

7 www.national.com

LM26

10132322

FIGURE 7. Audio Power Amplifier Thermal Protection

10132323

FIGURE 8. Simple Thermostat

www.national.com 8

LM26

Physical Dimensions inches (millimeters) unless otherwise noted

5-Lead Molded SOT-23 Plastic Package, JEDEC

Order Number LM26CIM5 or LM26CIM5X

NS Package Number MA05B

9 www.national.com

LM26

Notes

LM26 SOT-23, ±3°C Accurate, Factory Preset Thermostat

For more National Semiconductor product information and proven design tools, visit the following Web sites at:

Products Design Support

Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench

Audio www.national.com/audio Analog University www.national.com/AU

Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes

Data Converters www.national.com/adc Distributors www.national.com/contacts

Displays www.national.com/displays Green Compliance www.national.com/quality/green

Ethernet www.national.com/ethernet Packaging www.national.com/packaging

Interface www.national.com/interface Quality and Reliability www.national.com/quality

LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns

Power Management www.national.com/power Feedback www.national.com/feedback

Switching Regulators www.national.com/switchers

LDOs www.national.com/ldo

LED Lighting www.national.com/led

PowerWise www.national.com/powerwise

Serial Digital Interface (SDI) www.national.com/sdi

Temperature Sensors www.national.com/tempsensors

Wireless (PLL/VCO) www.national.com/wireless

THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION

(“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY

OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO

SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS,

IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS

DOCUMENT.

TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT

NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL

PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR

APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND

APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE

NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS.

EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO

LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE

AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR

PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY

RIGHT.

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR

SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

Life support devices or systems are devices 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. A critical component is any component in 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.

National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other

brand or product names may be trademarks or registered trademarks of their respective holders.

For the most current product information visit us at www.national.com

National Semiconductor

Americas Technical

Support Center

Email: support@nsc.com

Tel: 1-800-272-9959

National Semiconductor Europe

Technical Support Center

Email: europe.support@nsc.com

German Tel: +49 (0) 180 5010 771

English Tel: +44 (0) 870 850 4288

National Semiconductor Asia

Pacific Technical Support Center

Email: ap.support@nsc.com

National Semiconductor Japan

Technical Support Center

Email: jpn.feedback@nsc.com