1. Overview & Purpose:

️· What it is: The TJA1145 is a high-speed CAN transceiver IC designed for automotive and industrial applications.
️· Key Feature: It provides ISO 11898-2:2016 compliance, including support for selective wake-up functionality and autonomous bus biasing.
️· Purpose: To facilitate reliable CAN communication at speeds up to 1 Mbit/s (and supports CAN FD at up to 2 Mbit/s).

2. Operating Modes (Overall TJA1145 Modes):

️· Off: All functions disabled.
️· Standby: Some functions active, but CAN transceiver is in Offline or Offline Bias mode.
️· Normal: The primary operating mode for active communication. CAN operating mode is selectable.
️· Sleep: Some functions active but the CAN transceiver is forced into Offline or Offline Bias mode.
️· Overtemp: Similar to Sleep but triggered by an overtemperature condition, resulting in a forced switch to a safe state.

3. CAN Operating Modes (Within the TJA1145):

️· Active: Transceiver can transmit and receive data. Requires VCC to be above a certain voltage.
️· Listen-only: Transceiver monitors the bus but does not transmit. Used when the node should 'listen' to messages but not participate actively.
️· Offline: The transceiver does not participate in data communication. However, it maintains bus biasing.
️· Offline Bias: Like Offline, but the bus is biased based on bus activity (2.5V if activity, GND otherwise). This is particularly useful for CAN partial networking.

4. Key Features & Technologies:

️· Autonomous CAN Biasing: The IC automatically biases the CAN bus to maintain a proper voltage level, minimizing electromagnetic interference and enabling CAN partial networking.
️· Selective Wake-up: Supports a feature to allow the CAN node to be put into a low-power state and woken up by a specific message on the bus.
️· CAN FD Support: Provides timing parameters for operation at speeds up to 2Mbit/s in CAN FD networks.
️· VCC Undervoltage Detection: Monitors the voltage on VCC and forces the transceiver into a safe state (Offline or Offline Bias) if the voltage drops too low.
️· TXD Monitoring: If TXD is held low, the CAN transceiver defaults to Listen-only mode.

5. Control Registers & Settings:

️· Mode Control Register (0x01): Selects the overall TJA1145 operating mode (Off, Standby, Normal, Sleep). Bits "MC" control this.
️· CAN Control Register: Selects the CAN operating mode (Active, Listen-only, Offline, Offline Bias). Bits "CMC" control this.
️· Main Status Register (0x03): Provides status information, including:
- FSMS: Indicates how the transition to Sleep mode occurred (SPI command or undervoltage).
- OTWS: Over Temperature Warning Status.
- NMS: Normal Mode Status.