December 2004
LM89
0.75˚C Accurate, Remote Diode and Local Digital
Temperature Sensor with Two-Wire Interface
n Offset register allows sensing a variety of thermal
diodes accurately
General Description
The LM89 is an 11-bit digital temperature sensor with a
2-wire System Management Bus (SMBus) serial interface.
The LM89 accurately measures its own temperature as well
as the temperature of an external device, such as processor
thermal diode or diode-connected transistor such as the
2N3904. The temperature of any ASIC can be accurately
determined using the LM89 as long as a dedicated diode
(semiconductor junction) is available on the target die. The
LM89 remote sensor accuracy of 0.75˚C is factory trimmed
for the series resistance and 1.0021 typical non-ideality fac-
n On-board local temperature sensing
n 10 bit plus sign remote diode temperature data format,
0.125 ˚C resolution
n T_CRIT_A output useful for system shutdown
n ALERT output supports SMBus 2.0 protocol
n SMBus 2.0 compatible interface, supports TIMEOUT
n 8-pin MSOP and SOIC packages
Key Specifications
tor of the Intel® Pentium 4 and the Mobile Pentium 4
™
j
j
j
Processor-M thermal diode. The LM89 has an Offset
register to allow measuring other diodes without
requiring continuous software management. Contact
Supply Voltage
3.0 V to 3.6 V
0.8 mA (typ)
Supply Current
Local Temp Accuracy (includes quantization error)
@
hardware.monitor.team nsc.com to obtain the latest data for
TA=25˚C to 125˚C
3.0 ˚C (max)
new processors.
j
Remote Diode Temp Accuracy (includes quantization
The LM89 and the LM89-1 have the same functions but
different SMBus slave addresses. This allows for one of
each to be on the bus at the same time.
error)
TA=30˚C,TD=80˚C
0.75 ˚C (max)
1.0 ˚C (max)
3.0 ˚C (max)
Activation of the ALERT output occurs when any tempera-
ture goes outside a preprogrammed window set by the HIGH
and LOW temperature limit registers or exceeds the T_CRIT
temperature limit. Activation of the T_CRIT_A occurs when
any temperature exceeds the T_CRIT programmed limit.
The LM89 is pin and register compatible with the LM86,
LM90, Analog Devices ADM1032 and Maxim MAX6657/8.
TA=30˚C to 50˚C, TD=60˚C to 100˚C
TA=0˚C to 85˚C, TD=25˚C to 125˚C
Applications
n Processor/Computer System Thermal Management
(e.g. Laptop, Desktop, Workstations, Server)
n Electronic Test Equipment
Features
n Office Electronics
n Accurately senses die temperature of remote ICs or
diode junctions
Simplified Block Diagram
20041501
™
Pentium is a trademark of Intel Corporation.
© 2004 National Semiconductor Corporation
DS200415
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