Data Sheet

10

Rev. 1.0, 2010-06-02

TLE8250G

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 continuos short

on CANH or CANL, the internal over-temperature protection switches off the bus transmitter.

5.2

Open Logic Pins

All logic input pins have internal pull-up resistor to

V

open or floating, the TLE8250G enters into the Stand-By mode per default. In Stand-By mode the output driver

stage of the TLE8250G is disabled, the bus biasing is shut off and the HS CAN transceiver TLE8250G will 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 it’s root cause in a locked-up

microcontroller or in a short on the printed circuit board for example. In Normal Operation mode, a logical “Low”

the output driver stage (see Figure 5). The receive unit is still active and the data on the bus are monitored at the

RxD output pin.

Figure 5

TxD Time-Out function

Figure 5 shows how the output driver stage is deactivated and activated again. A permanent “Low” signal on the

TxD input pin activates the TxD time-out function and deactivates the output driver stage. To release the output

driver stage after a TxD time-out event the TLE8250G requires a signal change on the TxD input pin from logical

“Low” to logical “High”.

5.4

Under-Voltage detection

The HS CAN Transceiver TLE8250G is equipped with an under-voltage detection on the power supply

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case of an under-voltage event on

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the Stand-By mode, regardless of the logical signal on the pins NEN and NRM (see Figure 6). If the transceiver

TLE8250G recovers from the under-voltage event, the operation mode returns to the programmed mode by the

logical pins NEN and NRM.