What Is the Per-Channel Current Output of an NI 651x Digital I/O Device?

Issue Details

There are different values in the user manual for how much current an NI 651x device can source. What do these different values mean, and what is the actual current output for each channel on an NI 651x board?

Solution

The following table lists the derated current values for the PCI-6514 and PCI-6515 devices at a 100% duty cycle.
 

Ambient Temperature	PCI-6514, All Lines	PCI-6514, One Line per Port	PCI-6515, All Lines	PCI-6515, One Line per Port
Up to 25 °C	75 mA	350 mA	125 mA	475 mA
Up to 35 °C	65 mA	350 mA	125 mA	425 mA
Up to 45 °C	55 mA	350 mA	115 mA	375 mA
Up to 55 °C	50 mA	300 mA	100 mA	325 mA

For the 6514 at a temperature of 25 °C, if you are using all 8 lines in a port at the same time, a maximum of 75mA can be output from each line . Hence, the port can have a total maximum current output of 600mA (75mA x 8 = 600mA). If all 8 lines are not being used, the port can still output 600mA, but no one line can output more than 350mA. One example would be having line 0 draw 350mA, and line 1 draw 250mA. This would meet the current requirements for both the lines (350mA or less) and the entire port (600mA or less).

The same conclusion can be drawn for each of the other 651x devices respectively. Please make sure to observe the different current specifications for different temperature ranges, as well as PCI vs PXI. Below are tables taken from the help file for the 6516, 6517, 6518, and 6519. Please see the NI 651x User Manual (linked below) for the full specifications.

The following table lists the derated current values for the PCI-6516 and PCI-6517 devices at a 100% duty cycle.
 

Ambient Temperature	PCI-6516, All Lines	PCI-6516, One Line per Port	PCI-6517, All Lines	PCI-6517, One Line per Port
Up to 25 °C	75 mA	350 mA	125 mA	475 mA
Up to 35 °C	65 mA	350 mA	125 mA	425 mA
Up to 45 °C	55 mA	350 mA	115 mA	375 mA
Up to 55 °C	50 mA	350 mA	100mA	325 mA

The following table lists the derated current values for the PCI-6518 and PCI-6519 devices at a 100% duty cycle.
 

Ambient Temperature	PCI-6518, All Lines	PCI-6518, One Line per Port	PCI-6519, All Lines	PCI-6519, One Line per Port
Up to 25 °C	75 mA	350 mA	125 mA	475 mA
Up to 35 °C	65 mA	350 mA	125 mA	425 mA
Up to 45 °C	55 mA	350 mA	115 mA	375 mA
Up to 55 °C	50 mA	350 mA	100 mA	325 mA

Additional Information

The 651x devices do not regulate current output. You should respect the specified maximum output currents (which will depend on the output load and Vcc) to avoid any damage to the device.