18.1.4 Input/Output (LIN_TXD)

In Normal mode, the LIN_TXD pin is the microcontroller interface for controlling the state of the LIN_BUS output. LIN_TXD must be pulled to ground in order to drive the LIN bus low. If LIN_TXD is high, the LIN_BUS output transistor is turned off and the bus is in the Recessive state. If the LIN_TXD pin stays at LIN_V_SS level while switching into Normal mode, it must be pulled to a high level longer than 10 µs before the LIN Transceiver can be activated. This feature prevents the bus line from being accidentally driven to a Dominant state after Normal mode has been activated (also in case of a short circuit at LIN_TXD to LIN_V_SS). During Fail-Safe mode, this pin is used as an output and signals the Fail-Safe source.

The LIN_TXD pin provides a pull-down resistor in order to have a defined level if LIN_TXD is disconnected.

An internal timer prevents the bus line from being driven permanently in the Dominant state. If LIN_TXD is forced to low longer than t_dom > 20 ms, the LIN bus driver is switched to the Recessive state. Nevertheless, when switching to Sleep mode, the actual level at the LIN_TXD pin is relevant.

To reactivate the LIN bus driver, switch LIN_TXD to high (>10 µs).