LM90
鹵
3藲C Accurate, Remote Diode and Local Digital Temperature Sensor with Two-Wire
Interface
February 2002
LM90
鹵
3藲C Accurate, Remote Diode and Local Digital
Temperature Sensor with Two-Wire Interface
General Description
The LM90 is an 11-bit digital temperature sensor with a
2-wire System Management Bus (SMBus) serial interface.
The LM90 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 LM90 as long as a dedicated diode
(semiconductor junction) is available on the target die. The
LM90 remote sensor accuracy of
鹵
3藲C is factory trimmed for
the 1.008 typical non-ideality factor of the mobile Pentium
鈩?/div>
III thermal diode. The LM90 has an Offset
register to allow measuring other diodes without
requiring continuous software management. Contact
hardware.monitor.team
@
nsc.com to obtain the latest data for
new processors.
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 LM90 is pin and register compatible with the LM86,
Analog Devices ADM1032 and Maxim MAX6657/8.
n
On-board local temperature sensing
n
10 bit plus sign remote diode temperature data format,
0.125 藲C resolution
n
Diode fault detection circuitry
n
T_CRIT_A output useful for system shutdown (open
diode does not activate T_CRIT_A)
n
ALERT output supports SMBus 2.0 protocol
n
SMBus 2.0 compatible interface, supports TIMEOUT
n
8-pin MSOP packages
Key Specifications
j
Supply Voltage
j
Supply Current
3.0V to 3.6V
0.8mA (typ)
T
A
=25藲C to 125藲C
j
Local Temp Accuracy (includes quantization error)
鹵
4.0藲C (max)
j
Remote Diode Temp Accuracy (includes quantization
error)
T
A
=30藲C to 50藲C, T
D
=60藲C to 100藲C
T
A
=0藲C to 85藲C, T
D
=25藲C to 125藲C
鹵
3.0藲C (max)
鹵
4.0藲C (max)
Features
n
Accurately senses die temperature of remote ICs or
diode junctions
n
Offset register allows sensing a variety of thermal
diodes accurately
Applications
n
System Thermal Management
(e.g. Laptop, Desktop, Workstations, Server)
n
Electronic Test Equipment
n
Office Electronics
LM90 Simplified Block Diagram
20033701
Pentium
鈩?/div>
is a trademark of Intel Corporation.
漏 2002 National Semiconductor Corporation
DS200337
www.national.com
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