CanTransceivers

CAN tranceivers

The CAN transceiver interfaces to the CAN controller and to the CAN bus. Its task is to adapt the TTL level signals from the CAN controller to the signal levels on the CAN bus. Some price are collected at CanTransceiverPrices.

Different physical Layers are described in various ISO 11898 Documents

ISO11898-2 HighSpeed? CAN ISO11898-3 LowSpeedFaultTolerant? CAN ISO11898-5 LowPower? ISO11898-6 LowPowerSelectiveWakeUp?

A common transceiver for the physical layer defined by ISO 11898-2 (high-speed) is Philips 82C250 and (improved version) 82c251.

Other transceivers are TJA1054 for ISO 11898-3 (low-speed fault-tolerant CAN FaultTolerantCAN) and AU5790 (for SAE J2411 single-wire CAN).

More information about different physical layers are available at (http://www.can-cia.org/can/physical-layer/) http://www.can-cia.org/index.php?id=88

The question: "Are there any compatibility problems with using a mixed 3.3V and 5V transceiver network?" was answered by Steve Corrigan s-corrigan1@ti.com: "I have a bus with 30 3.3-V HVD230s and 30 5-V 82C250s and have no problems."

Some of the Philips transceivers, e.g. TJA1041, try to detect own problems by a feature called DOMINANT CLAMPING DETECTION. With this feature they introduce a low bit rate limit: TJA1041 Chapter TXD DOMINANT CLAMPING DETECTION: ..... The tdom(TXD) timer defines the minimum possible bit rate of 40 kbit/s.

Often it is required that the device electronic is galvanically decoupled from the CAN bus. In this case in the past opto couplers were used. These opto couplers are expensive and they add a noteworthy amount of propagation delay into the signal path. TI is offering dual-channel digital isolators with a very small amount of propagation delay of 16ns. inline:http://focus.ti.com/docs/prod/folders/print/iso7221m.html

CAN tranceivers integrated with the CAN controller

NXP announced the first micro controller with integrated CAN controller and physical layer transceiver in January 2011. The System-in-Package-solutions LPC11C22 and LPC11C24 with integrated Transceiver TJF1051 are offerd in LQFP48 housings.