AC82GL40-SLB95 Datasheet, PDF (87/98 Pages) Intel Corporation – Intel® Celeron® Mobile Processor Dual-Core on 45-nm Process

Thermal Specifications and Design Considerations
Table 28.
5.1.2
Thermal Diode Parameters Using Transistor Model
Symbol
Parameter
Min
Typ
Max
I_FW
I_E
n_Q
Beta
R_T
Forward Bias Current
Emitter Current
Transistor Ideality
Series Resistance
5
5
0.997
0.3
2.79
1.001
4.52
200
200
1.005
0.760
6.24
Unit
μA
μA
Ω
Notes
1,2
1
3,4,5
3,4
3,6
NOTES:
1.
Intel does not support or recommend operation of the thermal diode under reverse bias.
2.
Same as I_FW in Table 27.
3.
Characterized across a temperature range of 50-100°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:
I_C = I_S * (e ^qVBE^/nQ^kT –1)
where I_S = saturation current, q = electronic charge, V_BE = voltage across the transistor
base emitter junction (same nodes as VD), k = Boltzmann Constant, and T = absolute
temperature (Kelvin).
6.
The series resistance, R_T, provided in the Diode Model Table (Table 27) can be used for
more accurate readings as needed.
When calculating a temperature based on the 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 are capable of
also measuring the series resistance. Calculating the temperature is then accomplished
using the equations listed under Table 27. In most 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 diode ideality deviates from that of the n_trim, each
calculated temperature offsets by a fixed amount. This temperature offset can be
calculated with the equation:
T_error(nf) = T_measured * (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.
Thermal Diode Offset
In order to improve the accuracy of the diode-based temperature measurements, a
temperature offset value (specified as Toffset) is programmed in the processor MSR
which contains thermal diode characterization data. During manufacturing each
processor thermal diode is evaluated for its behavior relative to the theoretical diode.
Using the equation above, the temperature error created by the difference n_trim and the
actual ideality of the particular processor is calculated.
Datasheet
87