Copyright © 2015 Robot Circuits, LLC
23
RCAT-1A Rev A3 Designer’s manual
Serious Power for the Serious Designer
Note:
When using an external power source as shown above, it is required to make sure the power source return is
common with the RCAT™ ground since the mosfets flow the load current to ground. This sets-up the possibility
of flowing (relatively) large currents through the RCAT™ ground causing ground noise. Although the ground
plane on the board will mitigate most of this, it is still best if you connect the return line of your external power
source to a ground point on the RCAT™ that is as close to JP26 or JP27 as is possible.
The best options would be one of the ground access points on I/O connector J5 like the following:
Figure 20
This example shows the use of mosfet Q3 with the return line of the external power source tied to J5 pin 32-C
which connects the return line to the RCAT™ ground at a point very close to the Q3 source pin (see the yellow
arrows).
