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.
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