TJA1050 CAN Bus Transceiver Module

Interface between a CAN bus controller and the physical differential lines.

DESCRIPTION

The TJA1050 CAN Bus Transceiver Module provides the interface between a CAN bus controller and the physical CAN bus differential lines.

PACKAGE INCLUDES:

• TJA1050 CAN Bus Transceiver Module
• Male headers

KEY FEATURES OF TJA1050 CAN BUS TRANSCEIVER MODULE:

• Up to 1Mb/s bus speed
• Up to 1000 meter bus length
• 5V Operation

CAN stands for Controller Area Network and it is often thought of as primarily an automotive communication bus since it is the standard for use with automobiles to connect all the electronics and sensors together and is brought out to the outside world via the ODB-II interface.

The CAN bus is in fact a good communication bus for many applications that use multiple distributed MCUs which need to interact with each other such as in factory automation or robotics.

The key features of the CAN bus is that it uses only 2 wires for bus communications and all MCUs connect to these same 2 wires.

This module is mainly handy for providing the interface for connecting a built-in CAN bus controller as found in some of the more advanced MCUs, to the physical differential bus lines that connect the different MCUs on the bus.

CAN Bus Hardware Connections

The physical bus consists of two end nodes which sit at the two ends of the bus.  A cable of twisted pair wire which is usually shielded connect the two nodes.  For bench-top type use, any 2 wires will work to connect the nodes.   As the bus length increases or the environmental electrical noise increases, using twisted pair and adding shielding becomes more important.

The end nodes have a 120 ohm resistor that terminate the two ends of the bus.  Each of these modules have a built-in 120 ohm resistor at location R3.

Other nodes can be added between the two end nodes.  These can be spliced in-line or attached to the main bus using a short stub cable as long as the length is kept under 12″.  These additional nodes do not use a 120 ohm termination resistor and so the resistor on the module should be removed from these additional nodes.

Typical CAN Bus Arrangement

These modules have zero ohm resistors in series with the CANH/CANL bus lines that can be optionally use to add series resistance.  The module also has 2 small capacitors of approximately 30pF capacitance on these lines.

Module Connections

Since this module operates at 5V, if connecting to a 3.3V MCU a logic level translator will need to be used on the RX line going to the MCU.  Using one on the TX line is optional.

The module has the Select pin of the TJA1050 tied to ground which puts the transceiver into the high-speed mode which is the normal mode of operation.

The main MCU CAN controller connection is via a 4-pin male header.  The physical CAN bus is connected via a 2-pin male header.  The headers are shipped separately so these connections can be wired instead of using headers if desired.  The module will also fit the small 2.54mm screw terminals, but the terminal block will hang off the end of the board.

1 x 4 Header

• VCC =  5V power
• TX=  Transmit data input.  Reads in data from CAN controller and sends to bus lines
• RX=  Receive data output.  Reads out data from bus lines to the CAN controller
• GND=  Ground, connects to MCU ground.

1 x 2 Header

• CANH  =  CAN Bus H connection.  CANH connects to CANH on other modules
• CANL  =  CAN Bus L connection.  CANL connects to CANL on other modules

The module has 2 small M2 holes for mounting.

OUR EVALUATION RESULTS:

The CAN Bus is an underutilized bus and well worth exploring in the context of a distributed MCU system as it allows more of the system architecture to be moved to the software side of the equation which increases flexibility.  You don’t see cars having to have their CAN bus rewired every time some module is changed to add or remove a feature.  It is also very robust in order to survive the harsh automotive environment.

BEFORE THEY ARE SHIPPED, THESE MODULES ARE:

• Inspected
• Kitted with headers
• Packaged in a resealable ESD bag for protection and easy storage.

Notes: 

1. None

TECHNICAL SPECIFICATIONS