sbRIO Power Supply Limitations

[Nathan_B.]

We have a sbRIO-9626 and I am trying to figure out how to interpret the maximum current throuh the 3.3 and 5V rails of the RMC connector.  Does this mean that it will only be able to supply 1.5 Amps at 5 volts or does it mean that if I try to pull 1.5 amps it will try to supply it but something will get fried?

Also, when we were using a sbRIO-9632, it had a 2A non-replaceable fuse on the input line.  I couldn't find anything in the manual of the 9626.

[tannerite]

Nathan,

The sbRIO-9632 does have a non-replaceable fuse as does the sbRIO-9626 on the power supply front end. The customer should not need to know this is there, however, as they should be using a power supply that meets the sbRIO requirements. The fuse is to protect the rest of the board if there is a current surge from the external power supply. The front-end protection on sbRIO also includes reverse-voltage protection and some common-mode filtering. 9632 and 9626 front-end protection scheme is very similar.

The RMC 3.3V and 5V rails will not force the maximum current onto the customer's load -- this is not how current flow works. If the load needs to draw 0.1A, the sbRIO's power supply will supply the load with that. If the customer is using the 3.3V supply, that can draw a maximum of 0.25A and if they are using the 5V supply they can draw a maximum of 1.5A. Again, the power supply will not force the current to be 0.25A or 1.5A, respectively.

The the customer attempts to draw more than the maximum current specified in the user manual, they may cause damage to the power supply and sbRIO. We do not recommend drawing more than the maximum.

Best,

[Nathan_B.]

Ok, I see that it's a 10 amp fuse on the input which is much larger than the one on the 9632.