28
Intel
®
Celeron
®
D Processor in the 775-Land LGA Package
Thermal Design Guide
Order #303730
Thermal Management Logic and Thermal Monitor
T
ERROR
= T
MEASURED
* (1 - N
ACTUAL
/ N
TRIM
)
Where
T
ERROR
= correction factor to add to the reported temperature, T
MEASURED
= temperature
reported by the thermal sensor (Kelvin), N
ACTUAL
= the ideality factor of the on-die thermal
diode, N
TRIM
= the assumed ideality used by the thermal sensor. For the range of temperature
where the thermal diode is being measured, 30 - 80° C, this error term is nearly constant.
The value of N
TRIM
is available from the datasheet of the device measuring the processor on die
thermal diode. N
ACTUAL
can be assumed to be typical for this equation.
The series resistance, R
T
, is provided to allow for a more accurate measurement of the on-die
thermal diode temperature. R
T
, as defined, includes the processor pins but does not include 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
Equation 5.
T
ERROR
= (R
T
* (N – 1) * I
FW
min
) / (
nk/q
* I
N
ln
N)
Where
T
ERROR
= sensor temperature error,
N =
sensor current ratio,
k
= Boltzmann Constant,
q
=
electronic charge.
4.2.8
THERMTRIP# Signal
In the event of a catastrophic cooling failure, the processor will automatically shut down when the
silicon temperature has reached its operating limit. At this point the system bus signal
THERMTRIP# goes active and power must be removed from the processor. THERMTRIP#
activation is independent of processor activity and does not generate any bus cycles. Refer to the
processor datasheet for more information about THERMTRIP#.
The temperature where the THERMTRIP# signal goes active is individually calibrated during
manufacturing. The temperature where THERMTRIP# goes active is roughly parallel to the
thermal profile and greater than the PROCHOT# activation temperature. Once configured, the
temperature at which the THERMTRIP# signal is asserted is neither re-configurable nor accessible
to the system.
4.2.8.1
Cooling System Failure Warning
The PROCHOT# signal may be useful as an indication of cooling system failure. Messages could
be sent to the system administrator to warn of the cooling failure, while the thermal control circuit
would allow the system to continue functioning or allow a graceful system shutdown. If no thermal
management action is taken, the silicon temperature may exceed the operating limits, causing
THERMTRIP# to activate and shut down the processor. Regardless of the system design
requirements or thermal solution ability, the Thermal Monitor feature must still be enabled to
ensure proper processor operation.
