National Instruments NI USB-621x - Manual (Page 26)

Chapter 3 Connector Information
© National Instruments Corporation 3-3 NI USB-621x User Manual
+5 V Power as an Input
If you have high current loads for the digital outputs to drive, you can
exceed the 50 mA internal limit by connecting an external +5 V power
source to the +5 V terminals. These terminals are protected against
undervoltage and overvoltage, and they have a 350 mA self-resetting fuse
to protect them from short circuit conditions. If your USB-621x device has
more than one +5 V terminal, you can connect the external power supply to
one terminal and use the other as a power source.