ADLINK PCI-7224 - Manual (Page 40)

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• Operation Theorem
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 shorting 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.