AC82GL40-SLB95 Datasheet, PDF (85/98 Pages) Intel Corporation – Intel® Celeron® Mobile Processor Dual-Core on 45-nm Process

Thermal Specifications and Design Considerations
5.1.1
Table 26.
Thermal Diode
The processor incorporates an on-die PNP transistor whose base emitter junction is
used as a thermal diode, with its collector shorted to ground. The thermal diode can be
read by an off-die analog/digital converter (a thermal sensor) located on the
motherboard or a stand-alone measurement kit. The thermal diode may be used to
monitor the die temperature of the processor for thermal management or
instrumentation purposes but is not a reliable indication that the maximum operating
temperature of the processor has been reached. When using the thermal diode, a
temperature offset value must be read from a processor MSR and applied. See
Section 5.1.2 for more details. Please see Section 5.1.3 for thermal diode usage
recommendation when the PROCHOT# signal is not asserted.
The reading of the external thermal sensor (on the motherboard) connected
to the processor thermal diode signals does not reflect the temperature of the
hottest location on the die. This is due to inaccuracies in the external thermal
sensor, on-die temperature gradients between the location of the thermal diode and the
hottest location on the die, and time based variations in the die temperature
measurement. Time-based variations can occur when the sampling rate of the thermal
diode (by the thermal sensor) is slower than the rate at which the T_J temperature can
change.
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 the thermal control circuit. This temperature offset must be taken
into account when using the processor thermal diode to implement power management
events. This offset is different than the diode Toffset value programmed into the
processor Model Specific Register (MSR).
Table 26 to Table 29 provide the diode interface and specifications. The diode model
parameters apply to the traditional thermal sensors that use the diode equation to
determine the processor temperature. Transistor model parameters 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. Contact your external sensor
supplier for recommendations. The thermal diode is separate from the Intel Thermal
Monitor’s thermal sensor and cannot be used to predict the behavior of the Intel
Thermal Monitor.
Thermal Diode Interface
Signal Name
Pin/Ball Number
THERMDA
A24
THERMDC
A25
Signal Description
Thermal diode anode
Thermal diode cathode
Datasheet
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