1FEATURES
• Accurately Senses Die Temperature of Remote
ICs or Diode Junctions
• Offset Register Allows Sensing a Variety of
Thermal Diodes Accurately
• On-board Local Temperature Sensing
• 10 Bit Plus Sign Remote Diode Temperature
Data Format, 0.125°C Resolution
• Diode Fault Detection Circuitry
• T_CRIT_A Output Useful for System Shutdown
(Open Diode does not Activate T_CRIT_A)
• ALERT Output Supports SMBus 2.0 Protocol
• SMBus 2.0 Compatible Interface, Supports
TIMEOUT
• 8-pin VSSOP Package

APPLICATIONS
• System Thermal Management
(e.g. Laptop, Desktop, Workstations, Server)
• Electronic Test Equipment
• Office Electronics

KEY SPECIFICATIONS
• Supply Voltage 3.0 to 3.6 V
• Supply Current 0.8 mA (Typ)
• Local Temp Accuracy (Includes Quantization
Error)
– TA=25°C to 125°C, ±4.0 °C (Max)
• Remote Diode Temp Accuracy (Includes
Quantization Error)
– TA=30°C to 50°C, TD=60°C to 100°C, ±3.0 °C
(Max)
– TA=0°C to 85°C, TD=25°C to 125°C, ±4.0 °C
(Max)

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 ±3°C
is factory trimmed for the 1.008 typical non-ideality
factor of the mobile Pentium III thermal diode. The
LM90 has an Offset register to allow measuring other diodes without requiring continuous software
management.
Activation of the ALERT output occurs when any
temperature 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.