LM77 Datasheet | National Semiconductor

Description The LM77 is a digital temperature sensor and thermal window parator with an I2C™ Serial Bus interface. The window-parator architecture of the LM77 eases the design of temperature control systems conforming to the ACPI (Advanced Configuration and Power Interface) specification for personal puters. The open-drain Interrupt (INT) output bees active whenever temperature goes outside a programmable window, while a separate Critical Temperature Alarm (T_CRIT_A) output bees active when the temperature exceeds a programmable critical limit. The INT output can operate in either a parator or event mode, while the T_CRIT_A output operates in parator 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 puters, electronic test equipment, office electronics, automotive, and HVAC applications. Features n Window parison simplifies design of ACPI patible 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 LM77s can be connected to a single bus n 9-bit + sign output; full-scale reading of over 128˚C Key Specifications n Supply Voltage n Supply Current operating shutdown n Temperature Accuracy - 10˚C to 65˚C - 25˚C to 100˚C - 55˚C to 125˚C 3.0V to 5.5V 250 µA (typ) 500 µA (max) 5 µA (typ) ± 1.5˚C(max) ± 2˚C(max) ± 3˚C(max) Applications n n n n n n System Thermal Management Personal...