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LM27

SOT-23,

3˚C Accurate, 120˚C-150˚C Factory Preset

Thermostat

General Description

The LM27 is a precision, single digital-output, low-power

thermostat comprised of an internal reference, DAC, tem-

perature sensor and comparator. Utilizing factory program-

ming, it can be manufactured with different trip points as well

as different digital output functionality. The trip point (T

)

can be preset at the factory to any temperature in the range

of +120˚C to +150˚C in 1˚C increments. The LM27 has one

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

one analog output (V

TEMP

). The digital output stage can be

preset as either 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 tem-

perature shutdown event (OS or OS) or an under tempera-

ture shutdown event (US or US). When preset as an over-

temperature shutdown (OS) it will go LOW to indicate that

the die temperature is over the internally preset T

and go

HIGH when the temperature goes below (T

–T

HYST

). Simi-

larly, when preprogrammed as an undertemperature shut-

down (US) it will go HIGH to indicate that the temperature is

below T

and go LOW when the temperature is above

HYST

). The typical hysteresis, T

HYST

, can be set to

2˚C or 10˚C and is controlled by the state of the HYST pin. A

TEMP

analog output provides a voltage that is proportional

to temperature and has a −10.7mV/˚C output slope.

Currently, there are several standard parts available, see

ordering information for details. For other part options, con-

tact a National Semiconductor Distributor or Sales Repre-

sentative for information on minimum order qualification. The

LM27 is currently available in a 5-lead SOT-23 package.

Applications

n Microprocessor Thermal Management

n Appliances

n Portable Battery Powered Systems

n Fan Control

n Industrial Process Control

n HVAC Systems

n Electronic System Protection

Features

n Internal comparator with pin selectable 2˚C or 10˚C

hysteresis

n No external components required

n Open-drain or push-pull digital output; supports CMOS

logic levels

n Internal temperature sensor with V

TEMP

output pin

n V

TEMP

output allows after-assembly system testing

n Internal voltage reference and DAC for trip-point setting

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

n Excellent power supply noise rejection

Key Specifications

Power Supply Voltage 2.7V to 5.5V

Power Supply Current 40µA(max)

15µA(typ)

Hysteresis Temperature 2˚C or 10˚C(typ)

Temperature Trip Point Accuracy

3˚C (max)

LM27CIM5-2HJ Simplified Block Diagram and Connection Diagram

20030701

The LM27CIM5-2HJ has a fixed trip point of 140˚C.

For other trip point and output function availability,

please see ordering information or contact National Semiconductor.

August 2002

LM27 SOT-23,

3˚C Accurate, 120˚C-150˚C Factory Preset Thermostat

1 2 3 4 5 6 7 8 9

Indice de contenidos

Pagina 1 - Thermostat

LM27SOT-23,±3˚C Accurate, 120˚C-150˚C Factory PresetThermostatGeneral DescriptionThe LM27 is a precision, single digital-output, low-powerthermostat c

Pagina 2 - Pin Description

Ordering InformationFor more detailed information on the suffix meaning see the part number template at the end of the Electrical Characteris-tics Sec

Pagina 3 - Operating Ratings(Note 1)

Absolute Maximum Ratings (Note 1)Input Voltage 6.0VInput Current at any pin (Note 2) 5mAPackage Input Current(Note 2) 20mAPackage Dissipation at TA= 2

Pagina 4 - Part Number Template

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

Pagina 5 - Applications Hints

Functional DescriptionLM27 OPTIONSThe LM27 can be factory programmed to have a trip pointanywhere in-between 120˚C to 150˚C.Applications HintsAFTER-AS

Pagina 6 - 20030717

Applications Hints (Continued)TABLE 1. Resistive compensation for capacitiveloading of VTEMPCLOADR(Ω)≤100pF 01nF 820010nF 3000100nF 1000≥1µF 430NOISE

Pagina 7

Typical Applications20030703Note: The fan’s control pin has internal pull-up. The 10k pull-down sets a slow fan speed. When the output of the LM27 goe

Pagina 8 - FIGURE 8. Simple Thermostat

Typical Applications (Continued)20030722FIGURE 7. Audio Power Amplifier Thermal Protection20030723FIGURE 8. Simple ThermostatLM27www.national.com 8

Pagina 9 - LM27 SOT-23

Physical Dimensions inches (millimeters)unless otherwise noted5-Lead Molded SOT-23 Plastic Package, JEDECOrder Number LM27CIM5 or LM27CIM5XNS Package

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