8.1 Overview

The TCAN4420 is a high-speed CAN transceiver that meets the specifications of the ISO 11898-2 (2016) High Speed CAN (Controller Are Network) physical layer standards. It includes many protection features providing device and CAN network robustness. It also allows for the polarity of the CAN pins to be controlled externally by a micro-controller through the use of the polarity switch pin, SW.

The CAN bus has two logical states during operation: recessive and dominant. See Figure 6 and Figure 7.

A recessive bus state occurs when the bus is biased to a common mode of V_CC/2 via the receivers bias unit. Recessive is equivalent to logic high on the TXD pin and is typically a differential voltage on the bus of approximately 0 V.

A dominant bus state occurs when the bus is driven differentially by one or more drivers. The driver produces a current which flows through the termination resistors on the bus and generates a differential voltage. Dominant is equivalent to logic low on the TXD pin and is a differential voltage on the bus greater than the minimum required threshold for a CAN dominant.

The host microprocessor of the CAN node uses the TXD terminal, pin 1, to drive the bus and receives data from the bus via the RXD terminal, pin 4. The TCAN4420 integrates level shifting capabilities into the RXD output via the V_IO pin. This feature eliminates the need for an additional level shifter between the host microprocessor and the RXD output of the CAN transceiver.