User`s manual

34 Operation Theory
72XX Series
User’s Manual
4.4 12V and 5V Power Supply
The OPTO-22 compatible connectors provide external devices for
+12V and +5V power supply. To avoid shorting or overloading the
power supply, the resettable fuses are added on all the output
power. Refer to Figure 2.6.1
The maximum current for 5V on every connector is 0.5A. If the
load current is larger than this, the resistance of the resettable
fuse will increase due to the rise in temperature. This in turn will
cause the power supply to drop and reduce its current. If the short-
ing or overloading problem is eliminated, the fuse will return to its
normal condition. It is not necessary to repair or re-install the fuse.
The maximum current for 12V on all four connectors is also 0.5A.
The action of the fuse is the same as that used for +5V power. The
limitation is more restrictive than 5V power supply because the
PCI bus can not provide large amounts of current.