AppendixB CablingRequirements for PXI-8460 Low-Speed CAN
©NationalInstruments Corporation B-3 PXI-846xand NI-CAN for Windows NT
Connectingpin s2 and 3 of a ju mper configuresthe CAN p hysicallay er to
be poweredinternally (from the card). In this configuration, the V–signal
servesas the reference ground fort he isolated signals. Even if the CAN
physicallayer is powered internally, the fault-tolerant CAN transceiver still
requiresbus power to be supplied in order for it to monitor the power supply
(battery) voltage.
Figure B-3 showshow to configure your jumpers for internal or external
powersupplies.
FigureB-3. Power Source Jumpers
The CAN physical layer is still isolated regardless of the power source
chosen.
Bus Power Supply Requirements
Ift he CAN physical layer is poweredfrom a bus power supply, the power
supply should be a DC powersupply w ith an output of 8 V to 27 V.The
powerrequirements for the CAN ports for Bus-Powered configurations are
shownin Table B-1. Youshould take these requirements into account when
determining requirements of the bus powersupply for the system.
TableB-1. Power Requirements for the Low-Speed CAN Physical Layer
forBus-Powered Versions
Characteristic Specification
Voltagerequirement V+8–27 VDC
Currentrequirement 40 mA typical
100mA maximum
INT EXT
a.Internal Power Mode
INT EXT
b.External Power Mode
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