ANXL1250FYC3F AMD (ADVANCED MICRO DEVICES), ANXL1250FYC3F Datasheet - Page 67

• Manufacturer Part Number: ANXL1250FYC3F
• Manufacturer: AMD (ADVANCED MICRO DEVICES)

Specifications of ANXL1250FYC3F

• Lead Free Status / Rohs Status: Compliant

A.1
This section contains information about the calculations for
the on-die thermal diode of the AMD Geode™ NX proces-
sor. For electrical information about this thermal diode, see
Table 5-16 "Thermal Diode Electrical Characteristics" on
page 59.
A.1.1
The ideal diode equation uses the variables and constants
defined in Table A-1.
Equation 1 shows the ideal diode calculation.
Sourcing two currents and using Equation 1 derives the dif-
ference 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 ther-
mal diode temperature to be more accurate and less sus-
ceptible to die and process revisions. Temperature sensors
AMD Geode™ NX Processors Data Book
Appendix A: Thermal Diode Calculations
Table A-1. Constants and Variables for the Ideal
Equation
n
Symbol
f, lumped
V
I
I
q
T
k
BE
C
S
Thermal Diode Calculations
Ideal Diode Equation
V
BE
=
Variable, Constant Description
Lumped ideality factor
Boltzmann constant
Electron charge constant
Diode temperature (Kelvin)
Voltage from base to emitter
Collector current
Saturation current
Appendix
n
Diode Equation
f lumped
,
Equation 1.
⋅
-- - T
q
k
⋅
⋅
ln
⎛ ⎞
⎝ ⎠
I
--- -
I
C
S
ASupporting Documentation
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 calcu-
lating the temperature of a thermal diode.
A.1.2
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 tem-
perature sensor. The lumped ideality factor can be calcu-
lated using the equations in this section to find the
temperature offset that should be used with the tempera-
ture sensor.
Table A-2 shows the constants and variables used to calcu-
late the temperature offset correction.
Equation
n
T
Symbol
n
f, lumped
die, spec
Table A-2. Temperature Offset Equation
T
f, actual
n
I
I
offset
high
f, TS
low
Temperature Offset Correction
T
=
Constants and Variables
---------------------------------------------------------------- -
n
f lumped
,
Variable, Constant Description
Actual ideality factor
Lumped ideality factor
Ideality factor assumed by temperature
sensor
High sourcing current
Low sourcing current
Die temperature specification
Temperature offset
V
BE high
Equation 2.
,
⋅
-- -
q
k
–
⋅
V
ln
BE low
⎛
⎝
,
I
------- -
I
31177H
high
low
A
⎞
⎠
67