LM77 ±1.5°C Temperature Sensor with Alert Function and I2C/SMBus Interface | TI.com

This product has been released to the market and is available for purchase. For some products, newer alternatives may be available.
±1.5°C Temperature Sensor with Alert Function and I2C/SMBus Interface



The LM77 is a digital temperature sensor and thermal window comparator with an I2C 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.


  • 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

Key Specifications

  • Supply Voltage 3.0V to 5.5V
  • Supply Current
    • Operating250 μA (typ)500 μA (max)
    • Shutdown5 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)

All trademarks are the property of their respective owners.


Compare all products in Digital temperature sensors Email Download to Excel
Part number Order Device type Interface Local sensor accuracy (Max) (+/- C) Temp resolution (Max) (bits) Operating temperature range (C) Supply voltage (Min) (V) Supply voltage (Max) (V) Supply current (Max) (uA) Remote channels (#) Addresses Rating Package Group Package size: mm2:W x L (PKG) Approx. price (US$)
LM77 Order now Local     I2C, SMBus, 2-Wire     1.5     10     -55 to 125     3     5.5     500     0     4     Catalog     SOIC | 8
VSSOP | 8    
8SOIC: 19 mm2: 3.91 x 4.9 (SOIC | 8)
8VSSOP: 15 mm2: 4.9 x 3 (VSSOP | 8)    
0.95 | 1ku