Datasheet

TLE6251D
Fail Safe Functions
Data Sheet 13 Rev. 1.0, 2012-07-27
5.5 Overtemperature Protection
The TLE6251D has an integrated overtemperature detection circuit to protect the TLE6251D against thermal
overstress of the transmitter. The overtemperature protection is active in normal-operating mode and disabled in
stand-by mode. In case of an overtemperature condition, the temperature sensor will disable the transmitter (see
Figure 1) while the transceiver remains in normal-operating mode.
After the device cools down the transmitter is activated again (see Figure 8). A hysteresis is implemented within
the temperature sensor.
Figure 8 Overtemperature protection
5.6 Mode Changes during CAN Bus Failures
Failures on the CAN bus, like for example a short to the battery supply, might cause a permanent “dominant” signal
on the CAN bus and block the communication. Disregarding the signal on the CAN bus, the HS CAN transceiver
TLE6251D can change its operating mode from normal-operating mode to stand-by mode and vice versa.
While entering stand-by mode by setting the STB pin to logical “high”, the RxD output pin is set to logical “high”,
regardless if the CAN bus signal is “recessive” or “dominant”.
In stand-by mode the TLE6251D requires a mode change from “recessive” to “dominant” once, before the RxD
output follows the signals on the CAN bus. After detecting one signal change from “recessive” to “dominant” on
the CAN bus; a “recessive” CAN bus signal is indicated on the RxD output pin by a logical “high” signal and a
“dominant” CAN bus signal is indicated by a logical “low” signal, as long the pulse width of the CAN bus signals is
above the bus wake-up time t >
t
WU
(see Figure 9).
TxD
t
t
CANH
CANL
RxD
t
Overtemperature event
T
J
t
T
JSD
(shut-down temperature)
Cool Down
switch-on transmitter
ΔT