TLE6252G ,Fault Tolerant Differential CAN Trans...Features• Data transmission rate up to 125 kBaud• Very low current consumption in stand-by and slee ..
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TLE6252G
Fault Tolerant Differential CAN Trans...
Fault Tolerant Differential CAN Transceiver TLE6252 G
Target Data
FeaturesData transmission rate up to 125 kBaudVery low current consumption in stand-by and
sleep modeOptimized EMI behavior due to limited and
symmetric dynamic slopes of CANL and
CANH signalsSwitches to single-wire mode during bus line
failure eventsSupports one-wire transmission mode with ground offset voltages up to 1.5 VPreventation from bus occupation in case of CAN controller failureFully-integrated receiver filtersShort-circuit detection to battery and ground in 12V powered systemsThermal protectionBus line error protection against transients in automotive environment
� New type
Functional DescriptionThe CAN Transceiver works as the interface between the CAN protocol controller and
the physical differential CAN bus. Figure
1 shows the principle configuration of a CANnetwork.
The TLE 6252 is optimized for low-speed data transmission (up to 125kBaud) in
automotive and industrial applications.
In normal operation mode a differential signal is transmitted/received. When bus wiring
failures are detected the device automatically switches in single-wire mode to maintain
communication.
While no data is transferred, the power consumption can be minimized by multiple low
power modes.
TLE6252 G
Figure 1CAN Network Example
TLE6252 G
Pin Configuration(top view)
Figure 2
TLE6252 G
Table 1 Pin Definitions and Functions
TLE6252 G
Functional Block Diagram
Figure 3Block Diagram
TLE6252 G
General Operation Modes In addition to the normal operation mode, the CAN transceiver offers three multiple low
power operation modes to save power when there is no bus achieved: sleep mode, VBat
stand-by mode and VCC stand-by mode (see
Table2 and Figure4). Via the controlinputs NSTB and ENT the operation modes are selected by the CAN controller.
In sleep operation mode the lowest power consumption is achieved. To deactivate the
external voltage regulator for 5V supply, the INH output is switched to high impedance
in this mode. Also CANL is pulled-up to the battery voltage via the RTL output and the
pull-up paths at input pins TxD and RxD are disabled from the internal supply.
On a wake-up request either by bus line activities or by the input WAKE, the transceiver
automatically switches on the voltage regulator (5V supply). The WAKE input reacts to
rising and falling edges. As soon as VCC is provided, the wake-up request can be read
on both the NERR and RxD outputs, upon which the microcontroller can activate the
normal operation mode by setting the control inputs NSTB and ENT high.
In VCC-stand-by mode the wake up request is only reported at the RxD-output. The
NERR output in this mode is set low when the supply voltage at pin Vbat was below the
battery voltage threshold of 1V.
When entering the normal mode the Vbat-Flag is reseted and the NERR becomes high
again.
In addition the Vbat-Flag is set at a first connection of the device to battery voltage. This
feature is usefull e.g. when changing the ECU and therefore a presetting routine of the
microcontroller has to be started.
If either of the supply voltage drop below the specified limits, the transceiver
automatically goes to a stand-by mode.
TLE6252 G
Table 2Truth Table of the CAN TransceiverWake-up interrupts are released when entering normal operation mode.If go to sleep command was used before. ENT may turn LOW as V drops, without affecting internal functions.VBAT power-on flag will be reseted when entering normal operation mode.
TLE6252 G
Figure 4State DiagramThe transceiver will stay in a present operating mode until a suitable condition disposes
a state change. If not otherwise defined all conditions are AND-combined. The signalsCC and VBAT show if the supply is available (e.g. VCC = 1 : VCC voltage is present). If at
minimum one supply voltage is switched on, the start-up procedure begins (not figured).
TLE6252 G
Bus Failure ManagementThe TLE 6252 detects the bus failures as described in the following (Table
3, failureslisted according to ISO11519-2) and automatically switches to a dedicated CANH or
CANL single wire mode to maintain data transmission if necessary. Therefore, it is
equipped with one differential receiver and 4 single ended comparators, two for each bus
line. To avoid false triggering by external RF influences the single wire modes are
activated after a certain delay time. As soon as the bus failure disappears the transceiver
switches back to differential mode after another time delay. Bus failures are indicated in
the normal operation mode by setting the NERR output to LOW.
To reduce EMI the dynamic slopes of the CANL and CANH signals are both limited and
symmetric. This allows the use of an unshielded twisted or parallel pair of wires for the
bus. During single-wire transmission the EMI performance of the system is degraded
from the differential mode.
The differential receiver threshold is set to –2.8V. This ensures correct reception in the
normal operation mode as well as in the failure cases 1, 2 and 4 with a noise margin as
high as possible. For these failures, further failure management is not necessary.
Detection of the failure cases 1, 2 and 4 is only possible when the bus is dominant.
Nevertheless, they are reported on the NERR output until transmission of the next CAN
word on the bus begins.
When one of the bus failures 3, 5, 6, 6a and 7 is detected, the defective bus wire is
disabled by switching off the affected bus termination and the respective output stage. A
wake-up from sleep mode via the bus is possible either via a dominant CANH or CANL
line. This ensures that a wake-up is possible even if one of the failures 1 to 7 occurs.
In case the transmission data input, TxD from the CAN controller is permanently
dominant, both, the CANH and CANL transmitting stage, are deactivated after a delay
time. This is necessary to prevent blocking the bus by a defective protocol unit. The
transmit time out error is flagged on NERR.
TLE6252 G
Table 3Specified Wiring Failure Cases on the Bus Line 1)
(according to ISO11519-2)
Wire Interrupted
Wire Short-Circuited to GND
TLE6252 G
Wire Short-Circuited to Battery
CANL Mutually Short-Circuited to CANHThe images represent a communication between two participants of the network (see Figure
1). The controllerof the local area 1 transmits data (T×D1) to the receiver of the local area 2 (R×D2). When a single failure of
cases 1 to 7 occurs, the error handling enables communication through appreciated reactions.
Table 3Specified Wiring Failure Cases on the Bus Line (cont’d) 1)
(according to ISO11519-2)CANL
CANH
GNDV
AES02420
Failure case 7:
TxD1
TLE6252 G
Circuit ProtectionA current limiting circuit protects the CAN transceiver output stages from damage by
short-circuit to positive and negative battery voltages.
The CANH and CANL pins are protected against electrical transients which may occur
in the severe conditions of automotive environments.
The transmitter output stage generates the majority of the power dissipation. Therefore
it is disabled if the junction temperature exceeds the maximum value. This effectively
reduces power dissipation, and hence will lead to a lower chip temperature, while other
parts of the IC can remain operating.
Note:Maximum ratings are absolute ratings; exceeding one of these values may cause
Absolute Maximum RatingsVCC=0 to 5.5 V; VBAT > 0 V; t < 0.1 ms; load dumpSee ISO 7637Negative currents flowing out of the IC.Human body model: equivalent to discharging a 100 pF capacitor through a 1.5 kΩ resistor.
TLE6252 G
Operating Range
Thermal Resistance
