Data Sheet

13

Rev. 1.0

2016-07-15

TLE8250V

High Speed CAN Transceiver

Fail Safe Functions

5

Fail Safe Functions

5.1

Short Circuit Protection

The CANH and CANL bus outputs are short circuit proof, either against GND or a positive supply voltage. A

current limiting circuit protects the transceiver against damages. If the device is heating up due to a

continuous short on the CANH or CANL, the internal overtemperature protection switches off the bus

transmitter.

5.2

Unconnected Logic Pins

are open, the TLE8250VSJ enters into the power-save mode by default. In power-save mode the transmitter of

the TLE8250VSJ is disabled and the bus bias is floating.

5.3

TxD Time-out Function

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

TxD pin is continuously “low”. A continuous “low” signal on the TxD pin might have its root cause in a locked-

up microcontroller or in a short circuit on the printed circuit board, for example. In normal-operating mode, a

disables the transmitter (see Figure 8). The receiver is still active and the data on the bus continues to be

monitored by the RxD output pin.

Figure 8

TxD time-out function

Figure 8 illustrates how the transmitter is deactivated and activated again. A permanent “low” signal on the

TxD input pin activates the TxD time-out function and deactivates the transmitter. To release the transmitter

after a TxD time-out event the TLE8250VSJ requires a signal change on the TxD input pin from logical “low” to

logical “high”.

TxD

t

t

CANH

CANL

RxD

t

TxD time-out

TxD time–out released