Intel Pentium Mobile T2080 LF80539GE0301M Hoja De Datos
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LF80539GE0301M
Thermal Specifications and Design Considerations
66
Datasheet
When calculating a temperature based on thermal diode measurements, a number of
parameters must be either measured or assumed. Most devices measure the diode
ideality and assume a series resistance and ideality trim value, although some are
capable of also measuring the series resistance. Calculating the temperature is then
accomplished using the equations listed under
. In most temperature sensing
devices, an expected value for the diode ideality is designed-in to the temperature
calculation equation. If the designer of the temperature sensing device assumes a
perfect diode the ideality value (also called n
trim
) will be 1.000. Given that most diodes
are not perfect, the designers usually select an n
trim
value that more closely matches
the behavior of the diodes in the processor. If the processors diode ideality deviates
from that of n
trim
, each calculated temperature will be offset by a fixed amount. This
temperature offset can be calculated with the equation:
T
error(nf)
= T
measured
X (1 - n
actual
/n
trim
)
Where T
error(nf)
is the offset in degrees C, T
measured
is in Kelvin, n
actual
is the measured
ideality of the diode, and n
trim
is the diode ideality assumed by the temperature
sensing device.
5.1.2
Thermal Diode Offset
In order to improve the accuracy of diode based temperature measurements, a
temperature offset value (specified as Toffset) will be programmed into a processor
Model Specific Register (MSR) which will contain thermal diode characterization data.
During manufacturing each processors thermal diode will be evaluated for its behavior
relative to a theoretical diode. Using the equation above, the temperature error created
by the difference between n
trim
and the actual ideality of the particular processor will
be calculated.
If the n
If the n
trim
value used to calculate Toffset differs from the n
trim
value used in a
temperature sensing device, the T
error(nf)
may not be accurate. If desired, the Toffset
can be adjusted by calculating n
actual
and then recalculating the offset using the actual
n
trim
as defined in the temperature sensor manufacturers' datasheet.
The n
trim
used to calculate the Diode Correction Toffset are listed in
Table 21.
Thermal Diode n
trim
and Diode Correction Toffset
Symbol
Parameter
Unit
n
trim
Diode ideality used to calculate Toffset
1.01