TLE7257

Functional Description

Data Sheet

16

Rev. 1.0, 2013-10-16

4.9

TxD Time-out

The TxD time-out feature protects the LIN bus against permanent blocking in case the logical signal on the TxD

input is continuously “low”, caused by e.g. a malfunctioning microcontroller or a short circuit on the printed circuit

board. In Normal Operation mode, a logical “low” signal on the TxD input for the time

t

of the transmitter (see Figure 13). The receiver will remain active and the data on the bus are still monitored on

the RxD output.

The TLE7257 will release the output stage after a TxD time-out event first when detecting a logical “high” signal

on the TxD input for the time

t

Figure 13

TxD time-out

4.10

3.3 V and 5 V Logic Capability

The TLE7257 can be used for 3.3 V and 5 V microcontrollers. The logic inputs and the outputs are capable to

operate with both voltage levels. The RxD output needs an external pull-up resistor to the microcontroller supply

to define the voltage level (see Chapter 7.6 “RxD Pull-up Resistor” on Page 26 and Figure 16).

4.11

Short Circuit

The BUS pin of TLE7257 can withstand short circuits to either GND or to the

V

temperature protection may disable the transmitter in case of a permanent short circuit on the bus pin is causing

the overheating.

TLE7257_TXD_TIMEOUT

TxD

t

to,rec

t

TxD

TxD time-out due to e.g. microcontroller error

Release after TxD time-out

Recovery of the microcontroller error

Normal communication

Normal communication

V

BUS

t

t