LM95231 datasheet(8/20 Pages) NSC

8 / 20 page

Typical Performance Characteristics

Thermal Diode Capacitor or PCB Leakage Current Effect

Remote Diode Temperature Reading

Remote Temperature Reading Sensitivity to Thermal

Diode Filter Capacitance

20120205

20120207

Conversion Rate Effect on Average Power Supply

Current

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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.

The 2-wire serial interface, of the LM95231, is compatible

with SMBus 2.0 and I2C®. Please see the SMBus 2.0 speci-

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

LM95231 Datasheet(PDF) 8 Page - National Semiconductor (TI)

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