A M I S - 3 0 6 6 3
High Speed CAN Transceiver
Table 3: Function Table (X = don’t care)
Data Sheet
4.75 < V
CC
< 5.25V
Mode
High Speed
Pin
TxD
0
1
RxD
0
1
STATE
Dominant
Recessive
Bus
CANH
High
0.5 V
CC
CANL
Low
0.5 V
CC
V
CC
< PORL
Mode
-
Pin
TxD
X
RxD
1
STATE
Recessive
Bus
CANH
0 < V
CANH
< V
CC
CANL
0 < V
CANL
< V
CC
PORL < V
CC
< 4.75V
Mode
-
Pin
TxD
> V
IH
RxD
1
STATE
Recessive
Bus
CANH
0 < V
CANH
< V
CC
CANL
0 < V
CANL
< V
CC
7.3 Over-temperature Detection
A thermal protection circuit protects the IC from damage by switching off the transmitter if the junction temperature exceeds a value of approximately
160°C. Because the transmitter dissipates most of the power, the power dissipation and temperature of the IC is reduced. All other IC functions continue
to operate. The transmitter off-state resets when pin TxD goes HIGH. The thermal protection circuit is particularly needed when a bus line short circuits.
7.4 TxD Dominant Time-out Function
A TxD dominant time-out timer circuit prevents the bus lines from being driven to a permanent dominant state (blocking all network communication) if
pin TxD is forced permanently LOW by a hardware and/or software application failure. The timer is triggered by a negative edge on pin TxD. If the duration
of the LOW-level on pin TxD exceeds the internal timer value t
dom
, the transmitter is disabled, driving the bus into a recessive state. The timer is reset by a
positive edge on pin TxD.
7.5 Fail-safe Features
A current-limiting circuit protects the transmitter output stage from damage caused by accidental short circuit to either positive or negative supply voltage -
although power dissipation increases during this fault condition.
The pins CANH and CANL are protected from automotive electrical transients (according to "ISO 7637"; see Figure 4). Should TxD become disconnected,
this pin is pulled high internally. When the V
CC
supply is removed, pins TxD and RxD will be floating. This prevents the AMIS-30663 from being supplied
by the CAN controller through the I/O pins.
7.6 3.3V Interface
AMIS-30663 may be used to interface with 3.3V or 5V controllers by use of the V
33
pin. This pin may be supplied with 3.3V or 5V to have the corresponding
digital interface voltage levels.
When the V
33
pin is supplied at 2.5V, even interfacing with 2.5V CAN controllers is possible. See also Digital Output Characteristics @ V
33
= 2.5V, Table 7.
In this case a pull resistor from TxD to V
33
is necessary.
AMI Semiconductor - Rev. 1.4, Oct. 04
4
AMI [ AMI SEMICONDUCTOR ]
