Datasheet

Data Sheet 18 Rev. 1.1, 2011-06-06
TLE6251-3G
Fail Safe Features
7.2 Local Failures
If a local failure occurs during the operation of the TLE6251-3G, the devices sets an internal local failure flag. The
local failure flag can be displayed to the microcontroller during the Receive-Only mode and the failures are
indicated by a logical “Low” signal on the NERR pin. The following local failures can be detected:
• TxD time-out
• TxD to RxD Short
• RxD permanent Recessive Clamping
• Bus Dominant Clamping
• Over-Temperature Detection
7.2.1 TxD Time-Out Feature
The TxD time-out feature protects the CAN bus against permanent blocking in case the logical signal on the TxD
pin is continuously “Low”.
In Normal Operation mode, a logical “Low” signal on the TxD input pin for the time t > t
TXD
enables the TxD time-
out feature and the TLE6251-3G disables the output driver stage. In Receive-Only mode the TLE6251-3G
indicates the TxD time-out by a logical “Low” signal on the NERR pin (see Figure 10). To release the output driver
stage after the permanent “Low” signal on the TxD input pin disappears, a mode change from Receive-Only mode
to Normal Operation mode is required.
Figure 10 TxD Time-Out Feature
TxD
t
CANH
CANL
RxD
NSTB
t
TxD time-out
EN
NERR
Normal Operation mode
Normal Operation
mode
Receive-Only
mode
TxD time–out
released
Output stage
released
t
t
t
t = t
TXD