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CAN transceiver

With ±60-V fault protection

Published 2017-08-10

The MAX14883E transceiver is optimized for industrial applications. It features a ±60-V fault protection, a ±25-V functional common mode input range, and a ±10-kV ESD protection on the bus lines.

Block diagram of the MAX14883E high-speed transceiver, an evaluation board is available, too (Photo: Maxim)

The transceiver with selectable polarity by Maxim operates from a single 5-V supply (VCC) and includes a logic-level supply input (VL) for interfacing with 1,8-V to 5-V logic. The product features a polarity selection input (POL) that swaps the CAN_H and CAN_L lines, allowing for software correction of cross-wired field cables. Networks of up to 17 transceivers can operate up to 1 Mbit/s. Capacitive loading and other factors may limit the maximum speed. Networks of up to 120 transceivers can operate up to data rates of 125 kbit/s.

The chip includes a transmitter dominant timeout (tDOM) to prevent bus lockup caused by CAN controller error or by a fault on the TXD input. When TXD remains in the dominant state (low) for longer than tDOM, the driver is switched to the recessive state, releasing the bus. The component is available in an 8-pin SOIC package and operates over the -40 °C to +125 °C temperature range. CAN_H and CAN_L outputs are short-circuit current-limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs in a high-impedance state.

In multi-drop CAN networks, it is important to maintain a single linear bus of uniform impedance that is properly terminated at each end. A star configuration should never be used, recommends the chipmaker. Any deviation from the end-to-end wiring scheme creates a stub. High-speed data edges on a stub can create reflections back down the network. These reflections can cause data errors by eroding the noise margin of the system. Although stubs are unavoidable in a multi-drop system, care should be taken to keep these stubs as small as possible, especially when operating with high bit rates.

Maxim offers also an evaluation kit for its transceivers. It is an assembled and tested PCB (printed circuit board) that demonstrates the functionality of the MAX14833E fault-protected transceiver. The kit features 2,75-kV isolation between the CAN network and the CAN controller interface. It operates from a 3,3-V supply and an isolated 5-V supply.