LM81

LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor June 1999 LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor General Description The LM81 is a highly integrated data acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor-based system. In a PC, the LM81 can be used to monitor power supply voltages, temperatures, and fan speeds. Actual values for these inputs can be read at any time. Programmable WATCHDOG™ limits in the LM81 activate a fully programmable and maskable interrupt system with two outputs (INT and T_CRIT_). The LM81 has an on-chip digital output temperature sensor with 9-bit or 12-bit resolution, a 6 analog input ADC with 8-bit resolution and an 8-bit DAC. Two fan tachometer outputs can be measured with the LM81’s FAN1 and FAN2 inputs. The DAC, with a 0 to 1.25V output voltage range, can be used for fan speed control. Additional inputs are provided for Chassis Intrusion detection circuits, and VID monitor inputs. The LM81 has a Serial Bus interface that is compatible with SMBus™. n n n n n 2 fan speed monitoring inputs Chassis Intrusion Detector input WATCHDOG™ comparison of all monitored values SMBus Serial Bus interface compatibility VID0-VID4 monitoring inputs Key Specifications n Voltage monitoring Error n Temperature Error −40˚C to +125˚C n Supply Voltage Range n Supply Current n ADC and DAC Resolution n Temperature Resolution Operating: +2% (max) ± 3˚...