Appendix A
66
Digital Outputs
If you are using the high drive capability of any of the Data
Translation USB modules, ensure that the load is returned to the
digital ground provided in the connector next to the outputs.
If just eight of the digital outputs are switching 16 mA per output,
then 128 mA of current flows. To minimize problems with ringing,
loading, and EMI, a 22
Ω
resistor is used in series with all digital
outputs. You must consider this 22
Ω
resistor if you are matching
cable impedance to the far end.