Intel US15W Power Management, Power Measurement Support, Power Measurement Resistor, Equation

Power Management

3Power Management

3.1Power 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.

P = V 2

R

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

User’s Manual 21

Document Number: 320264