LM81 - Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor

Datasheet	Packaging	Samples & Pricing	Reliability	Design Tools	Application Notes	Knowledge Base

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

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

General Description

The LM81 is a highly integrated data acquisition system for hardware monitoring of servers, Personal Computers, or virtually any microprocessor-based system. More...

Applications

•	System Thermal and Hardware Monitoring for Servers and PCs
•	Office Electronics
•	Electronic Test Equipment and Instrumentation

Parameters Values

Temp Resolution 9-bit/0.5degC;12-bit/0.0625degC

TruTherm(TM) Beta Compensation No

Analog Inputs 6

ADC Resolution 8 bits

Fan Speed Inputs 2

Fan Control Output(s) 1 DAC

Fan Control Method Undefined

VID Inputs 5

Dynamic VID VCCP Monitoring Undefined

Bidirectional PROCHOT Support Undefined

GPIOs CI, RESET

Interrupt Outputs 2

Reference Voltage Undefined

Temperature Accuracy (+/-) 3 deg C

Temperature Min -40 deg C

Temperature Max 125 deg C

Interface Type SMBus

Supply Min 2.8 Volt

Supply Max 3.8 Volt

Quiescent Current 0.9 mA

Resolution 9 bits

Temperature Accuracy (+/-) 3 deg C

Additional Resources

Design Tools

Application Notes

Datasheet

RoHS Compliance Information	Size in Kbytes	Date
LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor	417 Kbytes	22-Feb-02	Download
LM81 Serial Interface ACPI-Compatible Microprocessor System Hardware Monitor (Japanese)	331 Kbytes

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Package Availability, Models, Samples & Pricing

Part Number

Package

Factory Lead Time

Models

Samples &
Electronic
Orders

Budgetary Pricing

Std
Pack
Size

Package
Marking
Format

Type

Pins

Spec.

MSL
Rating

Peak
Reflow

RoHS
Report

CAD
Symbols

Weeks

Qty

$US each

LM81BIMT-3

TSSOP

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$1.70

rail
of
61

NSUZXYTTE#
LM81
BIMT-3

8 weeks

500

LM81CIMT-3

TSSOP

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$1.70

rail
of
61

NSUZXYTTE#
LM81
CIMT-3

8 weeks

500

LM81BIMTX-3

TSSOP

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$1.70

reel
of
2500

NSUZXYTTE#
LM81
BIMT-3

8 weeks

7500

LM81CIMTX-3

TSSOP

NOPB
STD

1
1

260
260

RoHS

Download

Full production

N/A

1K+

$1.70

reel
of
2500

NSUZXYTTE#
LM81
CIMT-3

6 weeks

7500

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™.

Reliability Metrics

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

For more information on Reliability Metrics, please click here.

Design Tools

Title	Size in Kbytes	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	View	Download

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More Application Notes

Title	Size in Kbytes	Date
AN-1155: Application Note 1155 A Simple Software I2C Routine for the COP8	82 Kbytes	15-May-04	Download
AN-1260: Application Note 1260 Autonomous Fan Control for Processor Systems Using the LM85	74 Kbytes	10-Mar-04	Download
AN-1262: Application Note 1262 Four-Speed Fan Control Using Simple Remote Diode Temperature Sensor	70 Kbytes	1-Oct-02	Download
AN-1784: Application Note 1784 LMV1022 / LMV1023 Digital Output PDM Microphone Amplifier Demo Board User's Guide	3786 Kbytes	6-Mar-08	Download

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[Information as of 8-Nov-2009]