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Appendix C Cabling Requirements for PXI-8460 Low-Speed CAN
© National Instruments Corporation C-3 PXI-8461 or PXI-8460 and NI-CAN for Windows NT
Connecting pins 2 and 3 of a jumper configures the CAN physical layer to
be powered internally (from the card). In this configuration, the V– signal
serves as the reference ground for the isolated signals. Even if the CAN
physical layer is powered internally, the fault-tolerant CAN transceiver still
requires bus power to be supplied in order for it to monitor the power
supply (battery) voltage.
Figure C-3 shows how to configure your jumpers for internal or external
power supplies.
Figure C-3. Power Source Jumpers
The CAN physical layer is still isolated regardless of the power source
chosen.
Bus Power Supply Requirements
If the CAN physical layer is powered from a bus power supply, the power
supply should be a DC power supply with an output of 8 V to 27V. The
power requirements for the CAN ports for Bus-Powered configurations are
shown in Table C-1. You should take these requirements into account when
determining requirements of the bus power supply for the system.
Table C-1. Power Requirements for the Low-Speed CAN Physical Layer for
Bus-Powered Versions
Characteristic Specification
Voltage requirement V+ 8–27 VDC
Current requirement 40 mA typical
100 mA maximum
INT EXT
a. Internal Power Mode
INT EXT
b. External Power Mode
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