AMD AXDA3200DKV4E Data Sheet - Page 94
Temperature Offset Correction, Appendix A - Thermal Diode Calculations - specs
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Preliminary Information AMD Athlon™ XP Processor Model 10 Data Sheet 26237C-May 2003 Equation (1) shows the ideal diode calculation. VBE = nf, lumped ⋅ -kq ⋅ T ⋅ ln I-I--CS (1) 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. T = ---------V------B--E---,--h--i--g--h---------V-----B---E--,--l--o--w---------- nf, lumped ⋅ -kq ⋅ ln I-I--hl-oi--gw-h (2) 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