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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 2C™ 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 n Window comparison simplifies design of ACPI compatible 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 LM76s can be connected to a single bus n 12-bit + sign output; full-scale reading of over 127˚C Key Specifications n Supply Voltage 3.3V or 5.0V n Supply Current operating 250 µA (typ) 450 µA (max) shutdown 8 µA (max) n Temperature Accuracy +25˚C −10˚C to +45˚C ±0.5˚C(max) ±1.0˚C(max) 70˚C to 100˚C ±1.0˚C(max) n Resolution 0.0625˚C Applications n System Thermal Management n Personal Computers n Office Electronics n HVAC I2C® is a registered trademark of Philips Corporation. January 2000 © 2000 National Semiconductor Corporation DS101015 www.national.com |
