Isolated CAN Transceiver

The L41050 single-chip isolated CAN transceiver provides an isolated CAN interface in a single chip. Designed for harsh CAN and DeviceNet environments, the transceivers have a -55 to +125°C operating range, transmit data dominant time-out, bus pin transient protection, thermal shutdown protection, short-circuit protection, 2,500 volt isolation, and typical transient immunity of 30 kilovolts per microsecond. Unique edge-triggered inputs improve noise performance.

A unique non-volatile programmable power-up feature prevents unstable nodes. A state that needs to be present at node power up can be programmed at the last power down. For example if a CAN node is required to “pulse” dominant at power up, TxD can be sent low by the controller immediately prior to power down. When power is resumed, the node will immediately go dominant allowing self-check code in the microcontroller to verify node operation. If desired, the node can also power up silently by presetting the TxD line high at power down. At the next power on, the IL41050 will remain silent, awaiting a dominant state from the bus.

Isolating Standard CAN Transceivers

This simple circuit works with any CAN transceiver with a TxD dominant timeout, which includes all of the current-generation transceivers including the ubiquitous Philips/NXP TJA1050. Propagation delay is critical for CANbus, and the IL712 and IL721 bidirectional isolators have best-in-class propagation delay of 10 ns typical. This minimizes CAN loop delay and maximizes data rate over any given bus length, making IsoLoop Isolators ideal for CAN isolation. NVE also offers the smallest two-channel isolator, the IL712-1, in a unique MSOP-8.