Preliminary Information

AMD Athlon™ XP Processor Model 10 Data Sheet

26237C— May 2003

Equation (1) shows the ideal diode calculation.

VBE =

k

T ⋅ ln

IC

(1)

nf, lumped --

---

 

q

 

IS

 

Sourcing two currents and using Equation (1) derives the difference in the base-to-emitter voltage that leads to finding the diode temperature as shown in Equation (2). The use of dual sourcing currents allows the measurement of the thermal diode temperature to be more accurate and less susceptible to die and process revisions. Temperature sensors that utilize series resistance cancellation can use more than two sourcing currents and are suitable to be used with the AMD thermal diode. Equation (2) is the formula for calculating the temperature of a thermal diode.

TVBE, high VBE, low

=--------------------------------------------------------------

k

⋅ ln

Ihigh

(2)

nf, lumped --

-------

 

q

 

Ilow

 

Temperature Offset Correction

A temperature offset may be required to correct the value measured by a temperature sensor. An offset is necessary if a difference exists between the lumped ideality factor of the processor and the ideality factor assumed by the temperature sensor. The lumped ideality factor can be calculated using the equations in this section to find the temperature offset that should be used with the temperature sensor.

Table 29 shows the constants and variables used to calculate the temperature offset correction.

Table 29. Constants and Variables Used in Temperature Offset Equations

 

Equation Symbol

Variable, Constant Description

 

 

 

 

 

 

nf, actual

Actual ideality factor

 

 

nf, lumped

Lumped ideality factor

 

 

nf, TS

Ideality factor assumed by temperature sensor

 

 

Ihigh

High sourcing current

 

 

Ilow

Low sourcing current

 

 

Tdie, spec

Die temperature specification

 

 

Toffset

Temperature offset

 

82

Appendix A - Thermal Diode Calculations

Page 94
Image 94
AMD 10, 27493, 27488 manual Temperature Offset Correction