Intel Pentium 4 Processor in the 478-Pin Package Thermal Design Guidelines

Intel
®
Pentium
®
4 Processor in the 478-Pin Package Thermal Design Guidelines
R
28 Design Guide
8. Connect the heater resistor of TTV to a DC power supply. Connect current and voltage meters
as shown in the following figure.
Figure 10. Electrical Connection for Heater
V
+
_
+
_
Voltage Meter
Heater Resistor
I
DC
Power Supply
Current Meter
_
+
9. Refer to section 2.3.2 to setup the thermocouples used for T
A
measurement, and connect them
to a thermocouple meter.
10. Set the voltage of the DC power supply to the value calculated from the targeted power level
and the heater resistance, if the DC-power supplier uses a voltage-control mode
(e.g.,
PowerResistanceHeaterVoltage ×=
). Alternatively, an appropriate current can be
set to the DC-power supplier if the DC-power supplier uses a current-control mode.
11. The actual power applied to the heater resistor can be calculated by multiplying the readings
from the voltage meter and the current meter as shown in the figure in Step 8. As the heater
heats up, the heater resistance will increase slightly and the current will decrease resulting in a
small drop of power if a voltage-control mode is used. The power supply voltage has to be
increased to compensate for the drop in the current to maintain a constant power. Wait for one
hour to reach the stable condition before reading the case temperature (T
C
) and the local
ambient temperature (T
A
) from the thermocouples.
12. Calculate the case-to-ambient thermal relation resistance (θ
CA
) based on equation 1 given in
Section 2.2.2.2. This equation is shown below.
Θ
CA
= (T
C
- T
A
) / P
D
2.3.4.4 TTV Correction Factor to the Intel
®
Pentium
®
4 Processor in the 478-
Pin Package
Correction factors usually need to be applied to predict the thermal solution performance on the
real parts from thermal performance measured on a thermal test vehicle. Table 2 provides these
correction factors in the case of the TTV and the Intel

Pentium

4 processor in the 478-pin
package, and of the TTV. The value of a thermal resistance is derived from the value measured on
the TTV and the corresponding correction factor according to equation
{Processor Θ
CA
} = {TTV Θ
CA
} x Correction factor
This formula transposes to Θ
CS
and Θ
SA
.