Thermal Specifications and Design Considerations
processor temperature. Transistor Model parameters (Table 31) have been added to
support thermal sensors that use the transistor equation method. The Transistor Model
may provide more accurate temperature measurements when the diode ideality factor
is closer to the maximum or minimum limits. This thermal "diode" is separate from the
Thermal Monitor's thermal sensor and cannot be used to predict the behavior of the
Thermal Monitor.
Table 30.
Thermal “Diode” Parameters using Diode Model
Symbol
IFW
Parameter
Min
Typ
Max
Unit
Notes
1
Forward Bias Current
Diode Ideality Factor
Series Resistance
5
—
200
1.050
6.24
µA
-
2, 3, 4
2, 3, 5
n
1.000
2.79
1.009
4.52
RT
Ω
NOTES:
1. Intel does not support or recommend operation of the thermal diode under reverse bias.
2. Characterized across a temperature range of 50 – 80 °C.
3. Not 100% tested. Specified by design characterization.
4. The ideality factor, n, represents the deviation from ideal diode behavior as exemplified by the diode equation:
IFW = IS * (e qV /nkT –1)
D
where I = saturation current, q = electronic charge, V = voltage across the diode, k = Boltzmann Constant,
S
D
and T = absolute temperature (Kelvin).
5. The series resistance, R , is provided to allow for a more accurate measurement of the junction temperature.
T
R , as defined, includes the lands of the processor but does not include any socket resistance or board trace
T
resistance between the socket and the external remote diode thermal sensor. R can be used by remote diode
T
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:
Terror = [RT * (N-1) * IFWmin] / [nk/q * ln N]
where T
charge.
= sensor temperature error, N = sensor current ratio, k = Boltzmann Constant, q = electronic
error
Table 31.
Thermal “Diode” Parameters using Transistor Model
Symbol
IFW
Parameter
Min
Typ
Max
Unit
Notes
1, 2
Forward Bias Current
Emitter Current
5
—
—
200
200
µA
µA
—
—
Ω
IE
5
3, 4, 5
3, 4
nQ
Transistor Ideality
0.997
0.391
2.79
1.001
—
1.005
0.760
6.24
Beta
RT
3, 6
Series Resistance
4.52
NOTES:
1. Intel does not support or recommend operation of the thermal diode under reverse bias.
2. Same as IFW in Table 30.
3. Characterized across a temperature range of 50 – 80 °C.
4. Not 100% tested. Specified by design characterization.
5. The ideality factor, nQ, represents the deviation from ideal transistor model behavior as exemplified by the
equation for the collector current:
IC = IS * (e qV /n kT –1)
BE
Q
Where I = saturation current, q = electronic charge, V = voltage across the transistor base emitter junction
S
BE
(same nodes as VD), k = Boltzmann Constant, and T = absolute temperature (Kelvin).
6. The series resistance, R provided in the Diode Model Table (Table 30) can be used for more accurate readings
T,
as needed.
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
Datasheet
83
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