Intel
®
Celeron
®
Processor 1.66 GHz/1.83 GHz
January 2007
DS
Order Number: 315876-002
63
Thermal Specifications and Design Considerations—Intel
®
Celeron
®
Processor 1.66 GHz/1.83
GHz
Transistor Model may provide more accurate temperature measurements when the
diode ideality factor is closer to the maximum or minimum limits. Please contact your
external thermal sensor supplier for their recommendation. This thermal “diode” is
separate from the Thermal Monitor's thermal sensor and cannot be used to predict the
behavior of the Thermal Monitor.
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
Table 17
. 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
) is 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 processor’s diode ideality deviates from
that of n
trim
, each calculated temperature is 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.
Table 17.
Thermal Diode Interface
Signal Name
Pin/Ball Number
Signal Description
THERMDA
B22
Thermal diode anode
THERMDC
A22
Thermal diode cathode
Table 18.
Thermal “Diode” Parameters using Diode Mode
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
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.
2.
Characterized across a temperature range of 50 - 100°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.
