Datasheet

18

Rev. 1.11

2019-09-19

High Speed CAN Transceiver

TLE9251V

Fail safe functions

8

Fail safe functions

8.1

Short circuit protection

The CANH and CANL bus pins are proven to cope with a short circuit fault against GND and against the supply

voltages. 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.

8.2

Unconnected logic pins

All logic input pins have an internal pull-up current source to VIO. In case the VIO and VCC supply is activated and

the logical pins are open, the TLE9251V enters into the Stand-by mode by default.

8.3

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 logical “low” signal on the TxD pin for the time t > tTxD enables the TxD time-out

feature and the TLE9251V disables the transmitter (see Figure 13). The receiver is still active and the data on

the bus continues to be monitored by the RxD output pin.

Figure 13

TxD time-out function

Figure 13 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 TLE9251V requires a signal change on the TxD input pin from logical “low” to

logical “high”.

8.4

Overtemperature protection

The TLE9251V has an integrated overtemperature detection to protect the TLE9251V against thermal

overstress of the transmitter. The overtemperature protection is only active in Normal-operating mode. In

TxD

t

t

CANH

CANL

RxD

t

TxD time-out

TxD time–out released

t > tTxD