L9779WD datasheet(95/170 Pages) STMICROELECTRONICS

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L9779WD

Functional description

169

6.15

CAN transceiver

Figure 59. CAN transceiver diagram

6.15.1

CAN transceiver functionality description

The CAN bus transceiver allows the connection with a microcontroller through a high speed

CAN bus with transmission rates up to 1Mbit/s. The transceiver has one logic input pin

(CAN_TX), one logic output pin (CAN_RX) and two input/output pins for the electrical

connections to the two bus wires (CANH and CANL). The microcontroller sends data to the

CAN_TX pin and it receives data from the CAN_RX pin.

In case of power loss (VB pin disconnected) or ground loss (GND pins disconnected), the

transceiver doesn't disturb the communication of the remaining transceivers connected to

the bus. If CANL is shorted to ground, the transceiver is able to operate with reduced

EMI/RFI performances.

TX or RX=0 means Dominant state of CANH and CANL; TX or RX=1 means Recessive

state compliant to ISO11898-2.



Speed communication up to 1Mbit/s



Function range from +40 V to -18 V DC at CAN pins



GND disconnection fail safe at module level



GND shift operation at system level



ESD: Immunity against automotive transients per ISO7637 specification



Matched output slopes and propagation delay.

The CAN_TX signal is ignored (CAN to recessive state) until the RST pin is asserted.

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