CAN - Wiring - CANLAB

1 2003 esd gmbh Hannover CAN- Wiring Notes Rev. - WiringNotes on the Wiring of CAN-Bus Systems andthe Cable Selection 2003 esd gmbh Hannover CAN- Wiring Notes Rev. file:I:\texte\Doku\MANUALS\CAN\VERDRAHT\ Englisch\ of no. in the ChaptersThe changes in the user s manual listed below affect changes in the hardware, as well as changes inthe description of the facts versus previous graphic assignment of Combicon-style connector of available accessory technical changes are subject to change without notice. 2003 esd gmbh Hannover CAN- Wiring Notes Rev.

2 O T EThe information in this document has been carefully checked and is believed to be entirely reliable. esdmakes no warranty of any kind with regard to the material in this document, and assumes noresponsibility for any errors that may appear in this document. esd reserves the right to make changeswithout notice to this, or any of its products, to improve reliability, performance or assumes no responsibility for the use of any circuitry other than circuitry which is part of a productof esd does not convey to the purchaser of the product described herein any license under the patent rightsof esd gmbh nor the rights of electronic system design gmbhVahrenwalder Str.

3 20730165 HannoverGermanyPhone:+49-511-372 98-0 Fax:+49-511-372 / Canada:esd electronics Elm StreetHatfield, MA 2003 esd gmbh Hannover CAN- Wiring Notes Rev. Selecting Minimum Factors for the Selection of the Limit Values for Cable Cable Effective Resistance of the Effective Resistance of the Examples for Suitable Types of Bit Rate Depending on the Cable CiA Recommendation for Bit Timing (07/1995).. Reachable Line Lengths Via the 82. Wiring the Wiring and Connecting the 9-Pole Connecting the 5-Pole 143.

4 Available 15 2003 esd gmbh Hannover CAN- Wiring Notes Rev. page is intentionally left Cables 2003 esd gmbh Hannover CAN- Wiring Notes Rev. Selecting Minimum RequirementsThe boards and modules developed by esd use a differential two-wire system as a physical layer. Thelines used, must have at least two wires for the differential signals (CAN_H, CAN_L) and one wire forthe reference potential CAN_GND. If a shielded line is used, the shield should be assigned Factors for the Selection of the CableLine lengthShort lines (l < m), such as T-connectors, can be designed as flat ribboncable, if the external disturbances are low.

5 Generally, a shielded data-transferline with twisted wires for the differential signals is safer. Such lines shouldalways be used for cable lengths of more than rateDepending on the group delay times of the line, the possible total line length ofa CAN network increases with a decreasing bit rate (see chapter ).External disturbancesExternal disturbances, such as electromagnetic fields which are generated byother electric loads, must be considered. Critical are for instance powerfulelectric motors or other machines which can cause voltage variations in thesupply lines when being switched on or off.

6 If it cannot be avoided, for instance, to run the CAN line parallel to supply lineswhich have strong voltage variations, the use of double shielded lines for theCAN is characteristic impedance of the line used should be about 120 :. Byconnecting CAN participants, the characteristic impedance might change,though. Therefore, the characteristic impedance of the line used, should not resistanceThe resistor of the line used must be low enough to avoid that the voltage-operating point of the receive component at the end of the line is being fallenbelow.

7 For determining the voltage drop at the receiver the connectedterminating impedance is Cables 2003 esd gmbh Hannover CAN- Wiring Notes Rev. wire withtransposed wiresCAN_LCAN_HCAN_GND(at wire shield)120 Ohm120 Ohmearth (PE)Wire structureSignal assignment of wire and connection of earthing and = not connectedDSUB9 connector(female or male)pin designationconnector caseconnector caseDSUB9 connector(female or male)pin designationCAN wire with connectors120 OhmCAN_LCAN_HCAN_GNDS hield91469381467238 CAN_LCAN_HCAN_GND120 = not connected5275 Shield(at outer wire shield)(at inner wire shield)DSUB9 connector(female or male)pin designationDSUB9 connector(female or male)

8 Pin designationCAN wire with connectorsconnector caseconnector caseSignal assignment of wire and connection of earthing and terminatorDouble Shielded wire withtransposed wiresWire structureearth (PE)Do not connectto earthat this point ! Limit Values for Cable Cable GeometryIn order to eliminate external disturbances, data-transfer cables should generally be used which havetwo twisted signal wires and at least one shield for the reference : Geometry and connection of the single shielded CAN cableFig. : Geometry and connection of the double shielded CAN cableAt the double shielded line the user has to take special care that the outer shield is connected with theearth potential only via one connector housing.

9 Due to the connection of the connector housing togrounded front panels, the connection of pin5/connector housing to the outer shield has to realised atonly one point of the net (see above shown figure).This should be carried out at the same device at which the inner shield is also Cables 2003 esd gmbh Hannover CAN- Wiring Notes Rev. Effective Resistance of the CableThe ISO/DIS 11898 has the following recommendations for the DC voltage parameters, the terminatingimpedances and approximate values for the bit rate:Bus lengthCable 1*)TerminatingimpedanceMaximum bitrateResistivity permeterCross section of m70 mm , mm AW G 2 3 , AW G 2 2124 : / 1%1 Mbit/sat 40 m40 m.

10 300 m< 60 mm .. mm AW G 2 2 , AW G 2 0127 : / 1%2*)> 500 kbit/sat 100 m300 m .. 600 m< 40 mm , mm AWG20127 : / 1%2*)> 100 kbit/sat 500 m600 m ..1 km< 26 mm , mm AW G 1 8127 : / 1%2*)> 50 kbit/sat 1 km1*)Recommendation for AC parameters of the cable:- 120 : characteristic impedance- 5 ns/m delay time2*)It order to minimize the voltage losses caused by the effective resistance of the cable, a larger value for theterminating impedance (such as 150 : ..300 :, disregarding the norm ISO/DIS 11898, which here provides '118: < RT < 130 :') might be helpful for longer : Recommended DC voltage parameters depending on line Effective Resistance of the DSUB-ConnectorsWhen determining the voltage loss of the cable, the transfer resistance of the connectors have to beconsidered in addition to the cable resistance.