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Chapter 7 Power System
Calculating Power Usage
Use the worksheets in Tables 7-1 and 7-2 to calculate the total DC power
used by your system configuration.
The documentation that comes with each add-in board and peripheral
device should specify its current and voltage requirements.
To calculate the total combined wattage for your system, do this:
1. List the current for each board and device in the appropriate voltage
level column in Table 7-2.
2. Add the currents in each column of Table 7-2, and enter the total current
for each column in Table 7-1.
3. Multiply the voltage by the total current to get the total wattage for each
voltage level.
4. Add the total wattage for each voltage level to arrive at a total
combined power usage on the power supply.
✏
Note
The total combined wattage for your system configuration
must be less than 360 watts.
Table 7-1. Total Combined Power Used by Your System
Voltage Level and Total Current
(V X A = W)
Total Watts
for Each Voltage Level
(+3.3 V) X (______ A) ________ W
(+5 V) X (______ A) ________ W
(−5 V) X (______ A)
________ W
(+12 V) X (______ A) ________ W
(–12 V) X (______ A) ________ W
Total Combined Wattage ________ W