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Operation Theorem • 29
4.4 12V and 5V Power Supply
The OPTO-22 compatible connectors provide external devices the +12 volts
and +5 volts power supply. To avoid short or overload of the power supply,
resetable fuses are added on all the output power. Refer to Figure 2.5.
The maximum current for 5 volts on every connector is 0.5 A. If the load
current is larger than 0.5 A, the resistance of resetable fuse will increase
because of the rising temperature. The rising resistance will cause the
power supply drop and reduce current. If the overload or short condition is
removed, the fuse will get to normal condition. It is not necessary to repair
or re-install the fuse.
The maximum current of 12 volts for all the four connectors is also 0.5 A.
The action of the fuse is the same as which used for +5V power. The
limitation is more restrictive than 5V power supply because the PCI bus can
not provide large current.