LM95241

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SNIS143E – AUGUST 2006 – REVISED MARCH 2013

Processor Family

Diode Equation

Series R

min

typ

max

Pentium III CPUID 67h

1

1.0065

1.0125

Pentium III CPUID 68h/PGA370Socket/

1.0057

1.008

1.0125

Celeron

Pentium 4, 423 pin

0.9933

1.0045

1.0368

Pentium 4, 478 pin

0.9933

1.0045

1.0368

Pentium 4 on 0.13 micron process, 2-3.06GHz

1.0011

1.0021

1.0030

3.64

Ω

Pentium 4 on 90 nm process

1.0083

1.011

1.023

3.33

Ω

Pentium on 65 nm porcess

1.000

1.009

1.050

4.52

Ω

Pentium M Processor (Centrino)

1.00151

1.00220

1.00289

3.06

Ω

MMBT3904

1.003

AMD Athlon MP model 6

1.002

1.008

1.016

AMD Athlon 64

1.008

1.008

1.096

AMD Opteron

1.008

1.008

1.096

AMD Sempron

1.00261

0.93

Ω

Compensating for Different Non-Ideality

In order to compensate for the errors introduced by non-ideality, the temperature sensor is calibrated for a

particular processor. Texas Instruments temperature sensors are always calibrated to the typical non-ideality and

series resistance of a given processor type. The LM95241 is calibrated for two non-ideality factors and series

resistance values thus supporting the MMBT3904 transistor and the Intel processor on 65nm or 90nm process

without the requirement for additional trims. For most accurate measurements TruTherm mode should be turned

on when measuring the Intel processor on the 65nm or 90nm process to minimize the error introduced by the

false non-ideality spread (see Diode Non-Ideality Factor Effect on Accuracy). When a temperature sensor

calibrated for a particular processor type is used with a different processor type, additional errors are introduced.

Temperature errors associated with non-ideality of different processor types may be reduced in a specific

temperature range of concern through use of software calibration. Typical Non-ideality specification differences

cause a gain variation of the transfer function, therefore the center of the temperature range of interest should be

the target temperature for calibration purposes. The following equation can be used to calculate the temperature

LM95241.

where

•

•

•

(10)

The correction factor of Equation 10 should be directly added to the temperature reading produced by the

LM95233. For example when using the LM95241, with the 3904 mode selected, to measure a AMD Athlon

processor, with a typical non-ideality of 1.008, for a temperature range of 60 °C to 100 °C the correction factor

would calculate to:

(11)

Therefore, 1.75°C should be subtracted from the temperature readings of the LM95241 to compensate for the

differing typical non-ideality target.

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