The LM95231 is a precision dual remote diode temperature sensor (RDTS) that uses Texas
Instruments' TruTherm technology. The 2-wire serial interface of the LM95231 is compatible with
SMBus 2.0. The LM95231 can sense three temperature zones, it can measure the temperature of its own
die as well as two diode connected transistors. The LM95231 includes digital filtering and an
advanced input stage that includes analog filtering and TruTherm technology that reduces
processor-to-processor non-ideality spread. The diode connected transistors can be a “thermal
diode” as found in Intel and AMD processors or can simply be a diode connected MMBT3904 transistor.
TruTherm technology allows accurate measurement of “thermal diodes” found on small geometry
processes, 90nm and below. The LM95231 supports user selectable thermal diode non-ideality of
either a Pentium 4 processor on 90nm process or 2N3904.
The LM95231 resolution format for remote temperature readings can be programmed to be
11-bits signed or unsigned with the digital filtering disabled. When the filtering is enabled the
resolution increases to 13-bits signed or unsigned. In the unsigned mode the LM95231 remote diode
readings can resolve temperatures above 127°C. Local temperature readings have a resolution of
9-bits plus sign.
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