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.