Data Sheet

10

Rev. 1.0, 2010-09-03

TLE8250GVIO

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 TLE8250GVIO enters into the Stand-By mode per default. In Stand-By mode the output driver

stage of the TLE8250GVIO is disabled, the bus biasing is shut off and the HS CAN TLE8250GVIO transceiver 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 a short on the printed circuit board for example. In Normal Operation mode, a logical “Low”

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

RxD output pin.

Figure 5

TxD Time-Out function

Figure 5 shows the way how the transmission stage is deactivated and activated again. A permanent “Low” signal

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

the transmitter output stage after a TxD time-out event the TLE8250GVIO requires a signal change on the TxD

input pin from logical “Low” to logical “High”.