l4969 STMicroelectronics, l4969 Datasheet - Page 11

• Manufacturer Part Number: l4969
• Description: System Voltage Regulator With Fault Tolerant Low Speed Can-transceiver
• Manufacturer: STMicroelectronics

1.3
– Supports double wire unshielded busses
– Baud rate up to 125KBaud
– Short circuit protection (battery, ground, wires shorted)
– 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 def-
erentially (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). For low current consumption during bus inactivity a sleep mode
is available. The operating mode can be entered from the sleep mode either by local wake up ( C) or upon de-
tection of a dominant bit on the CAN-bus (external wake up).
Ten different errors on the physical buslines can be distinguished:
1.3.1 Detectable Physical Busline Failures
Not all of the 10 different errors lead to a breakdown of the whole communication.
So the errors can be categorized into 'negligible', 'problematic' and 'severe':
Errors caused by damage of the datalines or isolation
Errors caused by misbehavior of transceiver stage
Errors caused by defective protocol unit
VIII
VII
IV
VI
IX
III
N
V
X
II
I
CAN Transceiver
CANH wire interrupted (tied to Ground or termination)
CANL wire interrupted (floating or tied termination)
CANH short circuit to V
CANL short circuit to GND (permanently dominant)
CANH short circuit to GND (permanently recessive)
CANL short circuit to V
CANL shorted to CANH
CANH short circuit to VDD (permanently dominant)
CANL short circuit to VDD (permanently recessive)
CANH, CANL driven dominant for more than 1.3ms
BAT
BAT
Type of Errors
(overvoltage condition)
(overvoltage condition)
Edgecount difference > 3
Edgecount difference > 3
V(CANH) > 7.2V after 32us
V(CANL) < 3.1V & V(CANH)-V(CANL)
< -3.25V after 1.3ms
Edgecount difference > 3
V(CANL) > 7.2V after 32us
V(CANH) - V(CANL) < -3.25V after
1.3ms
V(CANH) > 1.8V & V(CANH) -
V(CANL) < -3.25V after 2.5ms
Edgecount difference > 3
Conditions
L4969
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