Rainbow Electronics LM76 User Manual

Lm76, General description, Features

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

Window comparison simplifies design of ACPI
compatible temperature monitoring and control.

Serial Bus interface

Separate open-drain outputs for Interrupt and Critical
Temperature shutdown

Shutdown mode to minimize power consumption

Up to 4 LM76s can be connected to a single bus

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

System Thermal Management

Personal Computers

Office Electronics

HVAC

I2C

is a registered trademark of Philips Corporation.

January 2000

LM76

0.5˚C,

1˚C,

12-Bit

Sign

Digital

emperature

Sensor

and

Thermal

indow

Comparator

with

wo-W

ire

Interface

DS101015