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L9669

1.

FUNCTIONAL DESCRIPTION

The L9669 is a monolithic integrated circuit which provides all main functions for an automotive body CAN sys-

tem. The device guarantees a clearly defined behavior in case of failure to avoid permanent CAN bus errors. It

is primarily intended for low speed applications in passenger cars.

1.1 Transceiver

– Supports double wire unshielded busses

– Baud rates up to 125 kBaud

– Single wire operation possible (automatic switching to single wire upon bus failures)

– Bus not loaded in case of unpowered transceiver

The CAN transceiver stage is able to transfer serial data on two independent communication wires either differ-

entially (normal operation) or in case of a single wire fault on the remaining line. The physical bitcoding is done

using dominant (transmitter active) and overwritable recessive states. Too long dominant phases are detected

internally and further transmission is automatically disabled (malfunction of protocol unit does not affect com-

munication on the bus (“fail safe mechanism”)).

1.2 Modes of Operation

Five different functional modes exist to enable or establish the usage of low power or receive only operation.

Note: Wake-up interrupts are released when entering RXonly or normal mode.

The following state diagram shows these modes and the possible state interactions depending on the input sig-

nals NSTB and EN.

NSTB

EN

Mode

INH

NERR

RXD

RTL

0

0

standby

VS

active LOW wake-up interrupt signal

(if VCC is present)

switched to VS

(typ. 13k

Ω)

0

0

sleep

floating

0

1

“go to sleep”

1

1

normal

VS

active LOW

error flag

HIGH=recessive

LOW=dominant

received data

switched to VCC

10

RXonly

Power on

active LOW

VS power-on

flag if VCC is

present

active LOW

wake-up interrupt

signal if VCC is

present

switched to VS