Thermal Specifications and Design Considerations
84 Dual-Core Intel® Xeon® Processor 3000 Series Datasheet
the "diode" parameter and interface specifications. Two different sets of "diode"
parameters are listed in Table 5-5 and Table 5-6. The Diode Model parameters
(Table 5-5) apply to traditional thermal sensors that use the Diode Equation to
determine the processor temperature. Transistor Model parameters (Table 5-6) 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.
T
CONTROL
is a temperature specification based on a temperature reading from the
thermal diode. The value for T
CONTROL
will be calibrated in manufacturing and
configured for each processor. The T
CONTROL
temperature for a given processor can be
obtained by reading a MSR in the processor. The T
CONTROL
value that is read from the
MSR needs to be converted from Hexadecimal to Decimal and added to a base value of
50 °C.
The value of T
CONTROL
may vary from 00 h to 1E h (0 to 30 °C).
When T
DIODE
is above T
CONTROL
then T
C
must be at or below T
C_MAX
as defined by the
thermal profile in Table 5-2; otherwise, the processor temperature can be maintained
at T
CONTROL
(or lower) as measured by the thermal diode.
NOTES:
1. Intel does not support or recommend operation of the thermal diode under reverse bias.
2. Preliminary data. Will be 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:
I
FW
= I
S
* (e
qV
D
/nkT
–1)
where I
S
= saturation current, q = electronic charge, V
D
= voltage across the diode, k =
Boltzmann Constant, and T = absolute temperature (Kelvin).
5. The series resistance, R
T
, is provided to allow for a more accurate measurement of the
junction temperature. R
T
, as defined, includes the lands of the processor but does not
include any socket resistance or board trace resistance between the socket and the
external remote diode thermal sensor. R
T
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:
T
error
= [R
T
* (N–1) * I
FWmin
] / [nk/q * ln N]
where T
error
= sensor temperature error, N = sensor current ratio, k = Boltzmann
Constant, q = electronic charge.
Table 5-5. Thermal “Diode” Parameters using Diode Model
Symbol Parameter Min Typ Max Unit Notes
I
FW
Forward Bias Current 5 — 200 µA 1
n Diode Ideality Factor 1.000 1.009 1.050 - 2, 3, 4
R
T
Series Resistance 2.79 4.52 6.24 Ω 2, 3, 5
