Power Measurements; Overview; Measurement Guidelines; Measure Voltage Across A Series Resistor - Intel PXA27 Series Design Manual

Power Measurements

5.1

Overview

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The Intel
management system that provides the best possible power utilization. Take additional steps to
minimize total power consumption. This chapter describes recommended methods for measuring
power and provides the recommended steps in detail to minimize overall power usage.
5.2

Measurement Guidelines

There are two methods for measuring power on each of the power domains of the PXA27x
processor:
•
Measuring voltage across a series resistor
•

Measure current directly with a current meter in series

The development design must allow for each power domain of the PXA27x processor to receive
power independently through a dedicated shunt jumper followed by a shunt resistor for each power
domain to use the two recommended methods.
No matter what method is used, measure the voltage at the PXA27x processor and monitor the
voltage across all power domains during each measurement.
5.2.1

Measure Voltage Across a Series Resistor

This method measures voltage across a series resistor and calculates the total power consumed.
This method involves using equipment to measure a voltage across a known series resistance and
calculating the current works for calculating power during normal mode operations. This method is
preferred for high current power supplies such as VCC_CORE. However, this method is not ideal
for measuring low power due to the limitations of the equipment being used to measure power. The
voltage drop when measuring low power could be too small for detection by the digital volt meter
(DVM).
5.2.2 Measure Current Directly with a Current Meter in Series
This method measures current directly with a current meter in series, then calculates total power
consumed. This methods works for all power modes, but could be too invasive and negatively
affect the functioning of the PXA27x processor in some cases.
Use the following procedure to measure current directly with a current meter is series:
1. Check the internal resistance for the current meter.
2. Calculate the effective voltage drop across the internal resistance based of the maximum
expected current.
3. Verify that the voltage drop minus the voltage supplying the voltage domain being tested does
not fall below the required V
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Intel PXA27x Processor Family Design Guide
PXA27x Processor Family (PXA27x processor) employs a complex power
for that domain.
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