Civil Engineering Reference
In-Depth Information
2.6.1.1
Pin Description
• WK: Local wake pin to wake up the transceiver from sleep mode via an external
switch on the ECU.
• INH: High-side switch to control the connected voltage regulator. On in non-
sleep mode and off in sleep mode.
• NSTB and ENT: Mode input pins to control the transceiver.
• NERR: Logic output pin to flag failure conditions.
• TxD: Transmit data input pin. The data on pin TxD will be transmitted on the bus
via CAN_H and CAN_L.
• RxD: Receive data output pin. The received data are formed into logic-level
signals for the microcontroller.
• CAN_H, CAN_L: Bus pins. Very robust high-voltage pins to transmit and re-
ceive data.
• RTL, RTH: Termination resistor switches. Off in case of bus failure and on in
failure-free mode.
• VS: Supply voltage pin (reverse polarity-protected battery supply).
• VCC: 5 V supply pin.
• GND: Ground connection.
2.6.1.2
Transmitter
The requirements on the transmitter according to voltage range, ESD robustness
and EMC performance are very high. To reduce emission during data transmission,
the symmetry of the CAN_H and CAN_L signals must be very high and the corners
must be rounded. This task will be done in driver of the output stage. The driver
stages CAN_H and CAN_L have to be very robust against ESD pulses. An ESD
pulse is very short, but during this time a current peak up to 20 A has to be handled
without any reduction on the driver performance. In case of a permanent dominant
signal on TxD (for example, caused by a short on pin TxD), the driver CAN_H and
CAN_L will be switched off to release the bus. The transceiver can now receive
data but cannot transmit data until the level on pin TxD is high. A high level on pin
TxD release the look and the transmitter can transmit again. The transmitter will be
also disabled in case of an over-temperature. After returning to the normal tempera-
ture range, the transceiver logic releases the transmitter automatically.
2.6.1.3
Receiver Block
The receiver block consists of five different comparators:
• Differential receiver: In normal operation, the differential comparator receives
the data.
• CAN_L comparator: Single-ended comparator to monitor CAN_L only.
