Measurement Computing USB-DIO24H/37, User Manual, Page: 10 / 16

USB-DIO24H/37 User's Guide Functional Details
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The following power limits depend on whether you are sourcing current out of the USB-DIO24H/37, or you are
sinking current into the USB-DIO24H/37.
Output (source) current limits
The maximum allowed current draw for a typical desktop computer and self-powered hub is 500 mA. You must
account for the supply current drawn from the USB supply for the USB-DIO24H/37 itself, plus the current used
by each DIO line. Since each DIO line can output 15 mA maximum, 24 DIO × 15 mA = 360 mA (maximum
rating for the chips).
Output (sink) current limits
Each USB-DIO24H/37 DIO output can sink up to 64 mA. For an individual line, this is not a problem. But if
you were to apply this maximum load to all 24 DIO lines, you would damage the USB-DIO24H/37 because the
total amount of current is well over the maximum for the USB supply.
If you want to sink the maximum of 64 mA per DIO line, you can only do so with up to six lines. To sink
current with all 24 DIO outputs at any one time, you can sink a maximum of 18 mA per line.
Mechanical Drawings
Figure 6. Circuit board dimensions