Thermal Specifications and Design Considerations
Offset between the thermal diode based temperature reading and the Intel Thermal
Monitor reading may be characterized using the Intel Thermal Monitor’s Automatic
mode activation of thermal control circuit. This temperature offset must be taken into
account when using the processor thermal diode to implement power management
events.
5.1.2
Thermal Diode Offset
A temperature offset value (specified as Toffset in Table 19) will be programmed into a
Celeron M processor Model Specific Register (MSR). This offset is determined by using a
thermal diode ideality factor mean value of n = 1.0022 (shown in Table 19) as a
reference. This offset must be applied to the junction temperature read by the thermal
diode. Any temperature adjustments due to differences between the reference ideality
value of 1.0022 and the default ideality values programmed into the on-board thermal
sensors, will have to be made before the above offset is applied.
Table 18.
Table 19.
Thermal Diode Interface
Signal Name
Pin/Ball Number
Signal Description
THERMDA
THERMDC
B18
A18
Thermal diode anode
Thermal diode cathode
Thermal Diode Specification
Symbol
Parameter
Min
Typ
Max
Unit
Notes
Note 1
IFW
Forward Bias Current
5
300
µA
Thermal Diode Temperature
Offset
Toffset
n
-4
11
°C
2, 6
Reference Diode Ideality Factor
Used to Calculate Temperature
Offset
Notes 2,
3, 4
1.0022
3.06
RT
Series Resistance
Ω
2, 3, 5
NOTES:
1.
Intel does not support or recommend operation of the thermal diode under reverse bias.
Intel does not support or recommend operation of the thermal diode when the processor
power supplies are not within their specified tolerance range.
Characterized at 100°C.
2.
3.
4.
Not 100% tested. Specified by design/characterization.
The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by
the diode equation:
I
FW=Is *(e(qVD/nkT) -1)
Where IS = saturation current, q = electronic charge, VD = voltage across the diode, k =
Boltzmann Constant, and T = absolute temperature (Kelvin).
Value shown in the table is not the Celeron M processor thermal diode ideality factor. It is a
reference value used to calculate the Celeron M thermal diode temperature offset.
The series resistance, RT, is provided to allow for a more accurate measurement of the
diode junction temperature. RT as defined includes the pins of the processor but does not
include any socket resistance or board trace resistance between the socket and the
external remote diode thermal sensor. RT can be used by remote diode thermal sensors
with automatic series resistance cancellation to calibrate out this error term. Another
application is that a temperature offset can be manually calculated and programmed into
an offset register in the remote diode thermal sensors as exemplified by the equation:
5.
6.
Terror = [RT*(N-1)*IFWmin]/[(no/q)*ln N]
Offset value is programmed in processor Model Specific Register.
66
Datasheet
INTEL [ INTEL ]
