Features • Temperature sensing • 6 positive voltage inputs with scaling resistors to monitor +5V, +12V, +3.3V, +2.5V, Vccp power supplies directly • 8-bit DAC output for controlling fan speed • 2 fan speed monitoring inputs • Chassis Intrusion detector input • WATCHDOG comparison of all monitored values • SMBus™ 1.0 (LM81C) and 1.1 (LM81B) Serial Bus interface compatibility • LM81B has improved voltage monitoring accuracy • VID0-VID4 monitoring inputs 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™. Key Specification Voltage Monitoring Error +2% or ±1.2% (max) Temperature Error -40°C to +125°C ± 3°C (max) Supply Voltage Range 2.8V to 3.8V Supply Current 0.4 mA (typ) ADC and DAC Resolution 8 Bits Temperature Resolution 0.5°C Applications • System Thermal and Hardware Monitoring for Servers and PCs • Office Electronics • Electronic Test Equipment and Instrumentation

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Datasheet

Title		Size	Date	Other Language
	LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor	417 Kbytes	22-Feb-02	日本語

Featured Application Notes

Title		Size	Date	Other Language
	AN-711: Application Note 711 LM78S40 Switching Voltage Regulator Applications	490 Kbytes	3-Oct-02

More Application Notes

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	AN-1155: Application Note 1155 A Simple Software I2C Routine for the COP8	82 Kbytes	15-May-04
	AN-1260: Application Note 1260 Autonomous Fan Control for Processor Systems Using the LM85	74 Kbytes	10-Mar-04
	AN-1262: Application Note 1262 Four-Speed Fan Control Using Simple Remote Diode Temperature Sensor	70 Kbytes	1-Oct-02
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Design Tools

Title	Size	Date
LMxx - Windows 95/98 VXD drivers with stand alone application for talking to temperature sensors or hardware monitors on a mother board	1366 Kbytes	28-Jul-2003

Reliability Metrics

Part Number	Process	EFR Reject	EFR Sample Size	PPM	LTA Rejects	LTA Device Hours	FITS	MTTF (Hours)
LM81BIMT-3	CS065	2	38968	52	0	4402000	1	1249079519
LM81BIMTX-3	CS065	2	38968	52	0	4402000	1	1249079519
LM81CIMT-3	CS065	2	38968	52	0	4402000	1	1249079519
LM81CIMTX-3	CS065	2	38968	52	0	4402000	1	1249079519

Note: The Early Failure Rates (EFR) were calculated as point estimate PPM based on rejects and sample size for EFR. The Long Term Failure Rates were calculated at 60% confidence using the Arrhenius equation at 0.7eV activation energy and derating the assumed stress temperature of 150°C to an application temperature of 55°C.

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