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Power Management
User’s Manual 21
Document Number: 320264
3 Power Management
3.1 Power Measurement Support
Power measurement resistors are provided to measure the power on many of the
subsystems.
Table 5. Power Measurement Resistor
Feature Value
Tolerance 1%
Value 10 mΩ
NOTE: Intel recommends that larger (~10 mΩ) resistors be stuffed for greater accuracy.
Power on a particular subsystem is calculated using the following formula:
Equation 1.
R
V
P
2
=
R = value of the sense resistor (typically 0.01 Ω)
V = the voltage difference measured across the sense resistor.
Use a high precision digital multi-meter tool such as the Agilent 34401A digital multi-
meter. Refer to Table 6
for a comparison of a high-precision, digital multi-meter
(Agilent 34401A) versus a precision, digital multi-meter (Fluke 79).
Table 6. Digital Multi-Meter Comparison
Example System
Sense Resistor Value 0.01 Ω
Voltage Difference Across Resistor 1.492 mV (149.2 mA)
Calculated Power 0.223 mW