Intel L2400 LE80539LF0282M User Manual

Datasheet

85

The processor incorporates three methods of monitoring die temperature, the digital 

thermal sensor (DTS), Intel Thermal Monitor and the thermal diode. The Intel Thermal 

Monitor (detailed in 

) must be used to determine when the maximum 

specified processor junction temperature has been reached.

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 Model Specific Register (MSR) 

and applied. See 

 for more details. Please see 

 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, will not necessarily 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 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).

, 

 provide the diode interface and 

specifications. Two different sets of diode parameters are listed in 

 and 

. The Diode Model parameters (

) apply to 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. Please contact your external thermal sensor supplier for their 

recommendation. This 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.

THERMDA

A24

Thermal diode anode

THERMDC

A25

Thermal diode cathode