1FEATURES

2• 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 LM77s Can be Connected to a Single

Bus

• 9-bit + Sign Output; Full-Scale Reading of Over

128°C

• SOIC and VSSOP 8-lead Packages

APPLICATIONS

• System Thermal Management

• Personal Computers

• Office Electronics

• Electronic Test Equipment

• Automotive

• HVAC

KEY SPECIFICATIONS

• Supply Voltage 3.0V to 5.5V

• Supply Current

– Operating

– 250 μA (typ)

– 500 μA (max)

– Shutdown

– 5 μA (typ)

• Temperature Accuracy

– −10°C to 65°C, ±1.5°C(max)

– −25°C to 100°C, ±2°C(max)

– −55°C to 125°C, ±3°C(max)

DESCRIPTION

The LM77 is a digital temperature sensor and thermal

window comparator with an I2 C Serial Bus interface.

The window-comparator architecture of the LM77

eases the design of temperature control systems

conforming to the ACPI (Advanced Configuration and

Power Interface) specification for personal

computers. The open-drain Interrupt (INT) output

becomes active whenever temperature goes outside

a programmable window, while a separate Critical

Temperature 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.

Programmable 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 thresholds of 2°C THYST, 10°C

TLOW, 64°C THIGH, and 80°C T_CRIT.

The LM77's 3.0V to 5.5V supply voltage range, Serial

Bus interface, 9-bit + sign output, and full-scale range

of over 128°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,

automotive, and HVAC applications.