Altera Arria V GT FPGA User Manual download pdf (Page 47)

Chapter 6: Board Test System 6–25

The Power Monitor

November 2012 Altera Corporation Arria V GT FPGA Development Kit

User Guide

f A table with the power rail information is available in the Arria V GT FPGA

Development Board Reference Manual.

Power Information

The Power information control displays current, maximum, and minimum power

readings for the following units:

■ mAmp

Power Graph

The power graph displays the mA power consumption of your board over time. The

green line indicates the current value. The red line indicates the maximum value read

since the last reset. The yellow line indicates the minimum value read since the last

reset.

Graph Settings

The following Graph settings controls allow you to define the look and feel of the

power graph:

■ Scale Select—Specifies the amount to scale the power graph. Select a smaller

number to zoom in to see finer detail. Select a larger number to zoom out to see the

entire range of recorded values.

■ Update Speed—Specifies how often to refresh the graph.

Reset

This Reset control clears the graph, resets the minimum and maximum values, and

restarts the Power Monitor.

Calculating Power

The Power Monitor calculates power by measuring two different voltages with the

LT2418 A/D and applying the equation P = V × I to determine the power

consumption. The LT2418 measures the voltage after the appropriate sense resistor

(Vsense) and the voltage drop across that sense resistor (Vdif). The current (I) is

calculated by dividing the measured voltage drop across the resistor by the value of

the sense resistor (I = Vdif/R). Through substitution, the equation for calculating

power becomes P = V × I = Vsense × (Vdif/R) = (Vsense) × (Vdif) × (1/.003), except for

the A5A_VCCINT and A5B_VCCINT rails which uses 0.001 Ohms for R and

A5A_VCCD_PLL_1.5V and A5B_VCCD_PLL_1.5V, which use 0.009 Ohms.

You can verify the power numbers shown in the Power Monitor with a digital

multimeter that is capable of measuring microvolts to ensure you have enough

significant digits for an accurate calculation. Measure the voltage on one side of the

resistor (the side opposite the power source) and then measure the voltage on the

other side. The first measurement is Vsense and the difference between the two

measurements is Vdif. Plug the values into the equation to determine the power

consumption.

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Altera Arria V GT FPGA User Manual Page 47