TLE6255G Datasheet, PDF (6/23 Pages) Infineon Technologies AG – Single Wire CAN-Transceiver

TLE 6255 G
Normal Mode
In the normal mode the TLE 6255 G sends a normal voltage message waveform on the
bus. It is possible to run the transceiver up to transmission rates of 33 kBits/s in this
mode.
The waveform as well as the slew rate of the rising edge (recessive to dominant
transition) are controlled by the internal active wave shaping circuit to minimize EME
(electromagnetic emission). For the same reason waveform trailing edge control is
required to assure that high frequency content is minimized at the beginning of the
downward voltage slope (dominant to recessive transition). The remaining fall time
occurs after the bus is inactive with drivers off and is determined by the RC time constant
of the total bus load.
6.2
Slew-Rate Control
The CANH output voltage and current is controlled by an internal waveshaping circuit.
For optimized adjusting of the slew rate to the system timing, the slew rate is
programmable by an external resistor connected from pin RSL to V_CC. Figure 4 shows
the correlation of the slew rate to the resistor R_RSL.
6.3
Transmitter
The TLE 6255 G contains a high current fully short circuit and overtemperature protected
highside-driver (pin CANH). To minimize spectral content the CANH-output waveform is
controlled.
Logic low (TxD = L) on pin TxD will command the output stage to switch to dominant high
potential; TxD = H to recessive low on the bus.
To avoid the bus to be blocked by a permanent dominant TxD input signal, the
TLE 6255 G incorporates a timeout feature. In case of TxD = L for longer than the
internal fixed timeout the CANH output is switched off automatically. The timeout is
resetted by a H-signal at TxD without a delay.
The loss of an ECU ground may cause the ECU to source current through the various
ECU circuits to the communications bus instead of to the vehicle system ground.
Therefore the unit-load resistor of any ECU is connected to the LOAD-pin. The
TLE 6255 G incorporates a reverse protected switch from LOAD to ground potential.
This switch is automatically switched off in a loss of ground state.
6.4
Receiver
In normal, high speed and wakeup-mode all data on the bus is sensed by the receive
comparator and transmitted to the RxD output. In sleep mode no normal level data is
detected. The receiver threshold is set to the wake-up level. So a wake-up interrupt is
sent only in case of a wake-up call on the bus. An internal fixed filter improves the EMC
susceptibility.
Data Sheet Rev. 2.5
6
2003-11-27