ICP DAS I-7531-FD Two-channel Isolated CAN FD Signal Repeater User Manual
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The I-7531-FD is a CAN/CAN FD signal repeater, which can connect two or more CAN networks with the same baud rate. Based on the signal repeat function of I-7531-FD, users can use different numbers of I-7531-FD to combine tree-shaped and star-shaped CAN network topology, and when there are too many devices on the CAN network, using I-7531-FD can increase the driving force of the CAN signal to drive more CAN devices. In addition, the CAN side of the I-7531-FD has a digital isolation of 2500 Vrms, and the CAN side and the power side also provide 3000 V DC-DC isolation protection, which can effectively isolate the noise interference between CAN networks ,and achieve protection the purpose of a specific CAN network.
- Supported CAN specification 2.0A/B and CAN FD
- Fully compatible with the ISO 11898-2 standard
- Detected CAN bus baud rate automatically, maximum support 8000 kbps
|Baud Rate||CAN bus: 5 k ~ 800 kbps
CAN FD: Arbitration rate up to 1000 kbps, data rate up to 8000 kbps
(Note) The data rates are verified by tests, but user-defined baud rates are possible, so the maximum data rate will depend on the concrete operating conditions (cable length, remote stations, etc.).
|Isolation||2500 Vrms for digital isolation, and 3000 V for DC-DC|
|Terminal Resistor||Build in 120 Ω terminal resistor and support jumper to select|
|Specification||ISO-11898-2, CAN 2.0A/B and CAN FD
(CAN FD support ISO and Non-ISO standards)
|Time Delay||Typ. 175ns (corresponds to ~35m CAN bus length)|
|Input Range||+10 VDC ~ +30 VDC|
|Dimensions (mm)||72 x 118 x 33 (W x L x H)|
|Operating Temperature||-25 ~ +75 °C|
|Storage Temperature||-30 ~ +80 °C|
|Humidity||10 ~ 90% RH, Non-condensing|
Figure 2 is a block diagram illustrating the functions of the I-7531-FD module. Power supply are with 3000 VDC galvanic isolated between each CAN port. Futhermore, there is digital-isolation 2500 Vrms between two CAN ports.
Figure2. Block Diagram
Table1. Pin Description
|1||CAN_L||CAN_Low. Signal Line of CAN port 1.|
|3||CAN_H||CAN_High. Signal Line of CAN port 1.|
|5||GND||CAN_Ground (or CAN_GND), voltage level of ground of CAN_L and CAN_H in CAN port 1.|
|9||(R)VS+||Power input +10VDC ~ +30VDC.|
|16||GND||CAN_Ground (or CAN_GND), Voltage level of ground of CAN_L and CAN_H in CAN port 2.|
|18||CAN_H||CAN_High. Signal Line of CAN port 2.|
|20||CAN_L||CAN_Low. Signal Line of CAN port 2.|
In normal situation, the CAN_GND does not need to be wired, but the CAN_GND’s voltage level of different CAN devices are not equal in some case. When in this situation, it maybe cause some problems and reduce the stability of the CAN bus system. The user can connect CAN_GND of these CAN devices to let the voltage level be same and eliminate this situation.
Electronic circuits are susceptible to electrostatic discharge (ESD) and will get worse when encountering continental climates, so F.G. provides a path for ESD to lead to the earth ground, thereby enhancing the module’s ability to protect against static electricity. If the user wants to use F.G., both pin 7 and pin 14 need to be connected to the earth ground, because the two pins are not connected inside the module.
Figure 5. Wire Connection
|OFF||No data in communication|
RUN LED’s twinkling rate correlates with baud rate of CAN bus.
User may see no twinkling when the twinkling period is too short because of the higher baud rate of CAN bus. Besides, the LED could look like always on when bus loading is heavy.
Terminator Resistor Setting
According to the ISO 11898-2 specifications, the bus line of CAN_H and CAN_L must be terminated by resistor for proper operation. The equivalent resistance between CAN_H and CAN_L should be 60Ω. There are some examples below.
Figure6. Terminator Resistor
On the other hand, the I-7531-FD module has built-in two 120Ω terminating resistors, and the user can use the jumper to select whether to enable it. Among them, JP1 is used to adjust the terminal resistance of CAN port 1, and JP2 is used to adjust the terminal resistance of CAN port 2. If the user wants to adjust the terminal resistance, who needs to open the casing of I-7531-FD, and will see the positions of JP1 and JP2 as shown in the figure below:
Figure7. JP1 and JP2 positions
The following connection statuses present the condition if the terminal resistor is enabled (default) or disabled.
Figure8. Adjustment of Terminator Resistor
Baud rate and wire length of CAN bus
The CAN bus is a balanced (differential) 2-wire interface running over either a Shielded Twisted Pair (STP), Un-shielded Twisted Pair (UTP), or Ribbon cable. However, the baud rate of communication is inversely proportional to the wire length. When the baud rate is lower, the ideal CAN bus wire length that can be used is longer, as shown in the following table.
(Note: The ideal CAN bus wire length means the sum of the wire lengths of each CAN bus in a single CAN network.)
Table2. Baud rate and ideal CAN bus wire lehgth
|Baud rate [bit/sec]||Ideal CAN bus wire length [meters]|
In addition, the I-7531-FD can isolate and re-amplify the CAN bus signal, so the user will think that connecting multiple I-7531-FDs in series on the same CAN bus, the CAN bus signal will always re-amplify and then extend the wire length of CAN bus, but the CAN bus signal passing through the I7531 FD will reduce the ideal CAN wire length due to the time delay at the physical layer in fact.
In other words, when the user add one I-7531-FD to the CAN bus, the CAN signal passing through the I-7531-FD will be delayed by 175ns, and the ideal CAN bus wire length will be reduced by 35 meters.
For example, the baud rate used by the user is 500Kbps, and the ideal CAN bus wire length is 100 meters, when one I-7531-FD is connected in series to the CAN bus, the ideal CAN bus wire length will be reduced by 35 meters that is reduced from 100 meters to 65 meters (100 – 35 x 1 = 65).
By analogy, if two I-7531-FDs are connected in series on the CAN bus, it will reduced by 35 x 2 = 70 meters as shown in the below figure.
Figure9. Differences after adding I-7531-FD
Therefore, the baud rate and the maximum number of I-7531-FD supported by a single CAN bus are shown in the following table.
Table3. The number of I-7531-FD supported by a single CAN bus
|Baud rate [bit/sec]||The number of I-7531-FD supported by a single CAN bus|
Documents / Resources
|ICP DAS I-7531-FD Two-channel Isolated CAN FD Signal Repeater [pdf] User Manual|
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