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accomplished using the equations listed under
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
are not perfect, the designers usually select an n
the behavior of the diodes in the processor. If the processors diode ideality deviates
from that of n
temperature offset can be calculated with the equation:
Where T
error(nf)
ideality of the diode, and n
sensing device.
To improve the accuracy of diode based temperature measurements, a new register
(T
diode_Offset
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
particular processor will be calculated. This value (T
to the new diode correction MSR and when added to the T
to correct temperatures read by diode based temperature sensing devices.
If the n
trim
temperature sensing device, the T
T
diode_Offset
the actual n
The Diode_Base value and n
listed in
Table
Table 32.
Thermal "Diode" n
Symbol
n
trim
Diode_Base
Table 33.
Thermal Diode Interface
Signal Name
THERMDA
THERMDC
84
, each calculated temperature will be offset by a fixed amount. This
trim
T
= T
error(nf)
measured
is the offset in degrees C, T
is the diode ideality assumed by the temperature
trim
) has been added to processor that will contain thermal diode
value used to calculate T
error(nf)
can be adjusted by calculating n
as defined in the temperature sensor manufacturers' datasheet.
trim
used to calculate the Diode_Correction_Offset are
trim
32.
and Diode_Correction_Offset
trim
Parameter
Diode ideality used to calculate Diode_Offset
Land Number
AL1
AK1
Thermal Specifications and Design Considerations
Table
30. In most temperature sensing
) will be 1.000. Given that most diodes
trim
value that more closely matches
trim
X (1 – n
/n
)
actual
trim
is in Kelvin, n
measured
trim
diode_Offset
differs from the n
diode_Offset
may not be accurate. If desired, the
and then recalculating the offset using
actual
Signal
Description
diode anode
diode cathode
§ §
is the measured
actual
and the actual ideality of the
) will be programmed in
value can be used
diode_Base
value used in a
trim
Unit
1.008
—
0
°C
Datasheet
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