LM95231_06 NSC [National Semiconductor], LM95231_06 Datasheet - Page 8

• Manufacturer Part Number: LM95231_06
• Description: Precision Dual Remote Diode Temperature Sensor with SMBus Interface and TruTherm Technology
• Manufacturer: NSC [National Semiconductor]

www.national.com
Typical Performance Characteristics
1.0 Functional Description
The LM95231 is a digital sensor that can sense the tempera-
ture of 3 thermal zones using a sigma-delta analog-to-digital
converter. It can measure its local die temperature and the
temperature of two external transistor junctions using a ∆V
temperature sensing method. The LM95231 can support two
external transistor types, a Pentium 4 processor on 90nm
process thermal diode or a 2N3904 diode connected tran-
sistor. The transistor type is register programmable and does
not require software intervention after initialization. The
LM95231 has an advanced input stage using National Semi-
conductor’s TruTherm technology that reduces the spread in
non-ideality found in Pentium 4 processors on 90nm pro-
cess. Internal analog filtering has been included in the ther-
mal diode input stage thus minimizing the need for external
thermal diode filter capacitors. In addition a digital filter has
been added. These noise immunity improvements in the
analog input stage along with the digital filtering will allow
longer trace tracks or cabling to the thermal diode than
previous thermal diode sensor devices.
Thermal Diode Capacitor or PCB Leakage Current Effect
Conversion Rate Effect on Average Power Supply
Remote Diode Temperature Reading
Current
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The 2-wire serial interface, of the LM95231, is compatible
with SMBus 2.0 and I2C
fication for a detailed description of the differences between
the I2C bus and SMBus.
The temperature conversion rate is programmable to allow
the user to optimize the current consumption of the LM95231
to the system requirements. The LM95231 can be placed in
shutdown to minimize power consumption when tempera-
ture data is not required. While in shutdown, a 1-shot con-
version mode allows system control of the conversion rate
for ultimate flexibility.
The remote diode temperature resolution is variable and
depends on whether the digital filter is activated. When the
digital filter is active the resolution is thirteen bits and is
programmable to 13-bits unsigned or 12-bits plus sign, with
a least-significant-bit (LSb) weight for both resolutions of
0.03125˚C. When the digital filter is inactive the resolution is
eleven bits and is programmable to 11-bits unsigned or
10-bits plus sign, with a least-significant-bit (LSb) weight for
both resolutions of 0.125˚C. The unsigned resolution allows
Remote Temperature Reading Sensitivity to Thermal
Diode Filter Capacitance
®
. Please see the SMBus 2.0 speci-
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