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LM76

0.5˚C,

1˚C, 12-Bit + Sign Digital Temperature Sensor

and Thermal Window Comparator with Two-Wire

Interface

General Description

The LM76 is a digital temperature sensor and thermal win-

dow comparator with an I

™

Serial Bus interface with an

accuracy of

1˚C. This accuracy for the LM76CHM is speci-

fied for a −10˚C to 45˚C temperature range, while for the

LM76CNM the temperature range is 70˚C to 100˚C. The

LM76CHM is specified with an accuracy

0.5˚C at 25˚C. The

window-comparator architecture of the LM76 eases the de-

sign of temperature control systems conforming to the ACPI

(Advanced Configuration and Power Interface) specification

for personal computers. The open-drain Interrupt (INT) out-

put becomes active whenever temperature goes outside a

programmable window, while a separate Critical Tempera-

ture Alarm (T_CRIT_A) output becomes active when the

temperature exceeds a programmable critical limit. The INT

output can operate in either a comparator or event mode,

while the T_CRIT_A output operates in comparator mode

only.

The host can program both the upper and lower limits of the

window as well as the critical temperature limit. Program-

mable hysterisis as well as a fault queue are available to

minimize false tripping. Two pins (A0, A1) are available for

address selection. The sensor powers up with default thresh-

olds of 2˚C T

HYST

, 10˚C T

LOW

, 64˚C T

HIGH

, and 80˚C

T_CRIT.

The LM76’s 3.3V and 5.0V supply voltage, Serial Bus inter-

face, 12-bit + sign output, and full-scale range of over 127˚C

make it ideal for a wide range of applications. These include

thermal management and protection applications in personal

computers, electronic test equipment, office electronics and

bio-medical applications.

Features

n Window comparison simplifies design of ACPI

compatible temperature monitoring and control.

n Serial Bus interface

n Separate open-drain outputs for Interrupt and Critical

Temperature shutdown

n Shutdown mode to minimize power consumption

n Up to 4 LM76s can be connected to a single bus

n 12-bit + sign output; full-scale reading of over 127˚C

Key Specifications

Supply Voltage 3.3V or 5.0V

Supply Current operating 250 µA (typ)

450 µA (max)

shutdown 8 µA (max)

Temperature

Accuracy

+25˚C

0.5˚C(max)

−10˚C to +45˚C

1.0˚C(max)

70˚C to 100˚C

1.0˚C(max)

Resolution 0.0625˚C

Applications

n System Thermal Management

n Personal Computers

n Office Electronics

n HVAC

is a registered trademark of Philips Corporation.

January 2000

LM76

0.5˚C,

1˚C, 12-Bit + Sign Digital Temperature Sensor and Thermal Window Comparator

with Two-Wire Interface

1 2 3 4 5 6 ... 14 15

Resumo do Conteúdo

Página 1 - Interface

LM76±0.5˚C,±1˚C, 12-Bit + Sign Digital Temperature Sensorand Thermal Window Comparator with Two-WireInterfaceGeneral DescriptionThe LM76 is a digital

Página 2 - Simplified Block Diagram

1.0 Functional Description (Continued)1.9 POINTER REGISTER(Selects which registers will be read from or written to):P7 P6 P5 P4 P3 P2 P1 P000000 Regis

Página 3 - Pin Description (Continued)

2.0 I2C Timing DiagramsDS101015-9Typical 2-Byte Read From Preset Pointer Location Such as Temp or Comparison RegistersDS101015-10Typical Pointer Set F

Página 4 - Operating Ratings(Notes 1, 5)

3.0 Application HintsThe temperature response graph inFigure 7depicts a typi-cal application designed to meet ACPI requirements. In thistype of applic

Página 5 - DS101015-4

3.0 Application Hints (Continued)4.0 Typical ApplicationsDS101015-15Note: Event Interrupt mode is drawn as if the user is reading the part. If the use

Página 6 - 1.0 Functional Description

4.0 Typical Applications (Continued)DS101015-19FIGURE 9. ACPI Compatible Terminal Alarm Shutdown. By powering the LM76 from auxilary output of the pow

Página 7 - DS101015-18

Physical Dimensions inches (millimeters) unless otherwise notedLIFE SUPPORT POLICYNATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENT

Página 8 - DS101015-6

Simplified Block DiagramConnection DiagramOrdering InformationOrder Number Supply Voltage AcurracyTemperatureRange forAccuracyTransport MediaLM76CHM-5

Página 9 - Figure 4

Pin Description (Continued)DS101015-3FIGURE 1. Typical ApplicationLM76www.national.com3

Página 10 - Section 1.1

Absolute Maximum Ratings (Note 1)Supply Voltage −0.3V to 6.5VVoltage at any Pin −0.3V to (+VS+ 0.3V)Input Current at any Pin 5mAPackage Input Current

Página 11 - C Timing Diagrams

Logic Electrical Characteristics (Continued)DIGITAL DC CHARACTERISTICS Unless otherwise noted, these specifications apply for for +VS=+3.3 Vdc±5% for

Página 12 - Figure 7

Logic Electrical Characteristics (Continued)Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC el

Página 13 - 4.0 Typical Applications

1.0 Functional Description (Continued)“True”: Temperature above a THIGHor T_CRIT is “true” forthose respective bits. A “true” for TLOWis temperature b

Página 14 - (Continued)

1.0 Functional Description (Continued)1.4 TEMPERATURE DATA FORMATTemperature data can be read from the Temperature and SetPoint registers; and written

Página 15 - NS Package Number M08A

1.0 Functional Description (Continued)and T_CRIT_A outputs. The fault queue is enabled by set-ting bit 4 of the Configuration Register high (see Secti

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