Part # LM81 datasheet

Part Manufacturer: National Semiconductor

National Semiconductor

Part Description: LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor

Part Details:

LM81 February 2002 Serial LM81Serial Interface ACPI-Compatible Microprocessor System InterfaceHardware MonitorGeneral Description n Chassis Intrusion detector input n WATCHDOG comparison of all monitored values The LM81 is a highly integrated data acquisition system for ACPI-Compatible hardware monitoring of servers, Personal Computers, or n SMBus 1.0 (LM81C) and 1.1 (LM81B) Serial Bus interface compatibility virtually any microprocessor-based system. In a PC, theLM81 can be used to monitor power supply voltages, tem- n LM81B has improved voltage monitoring accuracy peratures, and fan speeds. Actual values for these inputs n VID0-VID4 monitoring inputs can be read at any time. Programmable WATCHDOG limitsin the LM81 activate a fully programmable and maskable Key Specifications interrupt system with two outputs (INT and T_CRIT_). j Voltage Monitoring Error +2% or ±1.2% (max) The LM81 has an on-chip digital output temperature sensorwith 9-bit or 12-bit resolution, a 6 analog input ADC with 8-bit j Temperature Error resolution and an 8-bit DAC. Two fan tachometer outputs -40°C to +125°C ± 3°C (max) can be measured with the LM81 s FAN1 and FAN2 inputs. j Supply Voltage Range 2.8V to 3.8V The DAC, with a 0 to 1.25V output voltage range, can be j Supply Current 0.4 mA (typ) used for fan speed control. Additional inputs are provided for Microprocessor Chassis Intrusion detection circuits, and VID monitor inputs. j ADC and DAC Resolution 8 Bits The LM81 has a Serial Bus interface that is compatible with j Temperature Resolution 0.5°C SMBusTM. Applications Features n System Thermal and Hardware Monitoring for Servers n Temperature sensing and PCs n 6 positive voltage inputs with scaling resistors to monitor n Office Electronics +5V, +12V, +3.3V, +2.5V, Vccp power supplies directly n Electronic Test Equipment and Instrumentation n 8-bit DAC output for controlling fan speed n 2 fan speed monitoring inputs System Typical Application Hardware Monitor

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LM81.pdf Datasheet