Electro-Voice P3000RL owner manual Can-Bus, Cable Specifications, General Note

CAN-BUS

Baud Rate	Bus Length
500 kbit/s	100 m
250 kbit/s	250 m
125 kbit/s	500 m
62.5 kbit/s	1000 m
20 kbit/s	2500 m
10 kbit/s	5000 m

The CAN-bus allows using different data rates, with the data rate being indirectly proportional to the bus length. Small networks allow baud rates up to 500kbit/s.

For sizable dimensioned networks reducing the baud rate (minimum 10kbit/s) is necessary.

The integration of repeaters is generally recommended when the bus-length exceeds 1,000m.

CABLE SPECIFICATIONS

According to the ISO 11898-2 standard, CAN-bus data transfer cabling has to be carried out using Twisted-Pair cables with or without shielding providing a characteristic impedance of 120Ω. Both ends of a CAN-bus need to be terminated with 120Ω termination-plugs.

The maximum bus-length depends on the actual data transfer rate, the kind of data transfer cable being used, as well as the total number of participants on the bus. The following table shows the most essential coherencies for CAN-networks consisting of up 64 participants:

	Cable for data Transmission			max.
Bus Length			Termination
	Resistance per
		Cable Diameter		Data Transfer Rate
	Unit Length
0 ... 40 m	< 70 mΩ/m	0.25 ... 0.34 mm²	124 Ω	1000 kbit/s at 40 m
		AWG23, AWG22
40 ... 300 m	< 60 mΩ/m	0.34 ... 0.6 mm²	127 Ω	500 kbit/s at 100 m
		AWG22, AWG20
300 ... 600 m	< 40 mΩ/m	0.5 ... 0.6 mm²	150 Ω ... 300 Ω*	100 kbit/s at 500 m
		AWG20
600 ... 1000 m	< 26 mΩ/m	0.75 ... 0.8 mm²	150 Ω ... 300 Ω*	62.5 kbit/s at 1000 m
		AWG18

*With longer cables and many participants on the CAN-bus, termination resistors with higher impedance than the specified 120Ω are recommended to reduce the ohmic load of the interface drivers and therefore the voltage drop between the two cable ends.

The following table is meant for first assessment of necessary cable diameters for different bus lengths and bus-participant numbers:

Bus Length	Number of Appliance on the CAN-Bus
	32	64	100
100 m	0.25 mm² or AWG24	0.34 mm² or AWG22	0.34 mm² or AWG22
250 m	0.34 mm² or AWG22	0.5 mm² or AWG20	0.5 mm² or AWG20
500 m	0.75 mm² or AWG18	0.75 mm² or AWG18	1.0 mm² or AWG17

Additionally, the length of branch lines – for participants that are not directly connected to the CAN-bus

–is also of importance. For data transfer rates of up to 125kbit/s, the maximum length of a single stub cable should not exceed 2m. For higher bit rates a maximum length of only 0.3m is still permissible. The entire length of all branch lines should not exceed 30 m.

General Note:

As long as only short distances (up to 10m) are concerned, common RJ-45 patch cables with 100Ω characteristic impedance (AWG 24 / AWG 26) can be used for the cabling inside of a rack- shelf system. The previously outlined guidelines for network cabling are mandatory as far as the rack-shelve interconnection or fixed installations are involved.

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