Data Sheet

10

Rev. 1.0, 2012-03-14

TLE7250GVIO

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 damage. If the device heats 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

All logic input pins have an internal pull-up resistor to

V

are open or floating, the TLE7250GVIO enters the stand-by mode by default. In stand-by mode, the transmitter of

the TLE7250GVIO is disabled, the bus bias is connected to GND and the HS CAN TLE7250G transceiver does

not influence the data on the CAN bus.

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 can have its root cause in a locked-up

microcontroller or in a short on the printed circuit board for example. In the normal-operating mode, a logical “low”

transmitter (see Figure 5). The receiver is still active and the data on the bus continues to be monitored by the

RxD output pin.

Figure 5

TxD Time-out function

Figure 5 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 TLE7250GVIO requires a signal change on the TxD input pin from logical “low” to logical “high”.

5.4

Undervoltage Detection

The HS CAN transceiver TLE7250GVIO is provided with undervoltage detection at the power supply

V

the power supply

V

mode of TLE7250GVIO to the stand-by mode, regardless of the logical signal on the NEN pin (see Figure 6). If

the transceiver TLE7250GVIO recovers from the undervoltage condition, the operating mode is restored to the

programmed mode by the NEN pin.

TxD

t

t

CANH

CANL

RxD

t

TxD time-out

TxD time-out released