AMIS-30660 High Speed CAN Transceiver
7.0 Functional Description
The AMIS-30660 is the interface between the CAN protocol
controller and the physical bus. It is intended for use in
automotive and industrial applications requiring baud rates
up to 1 Mbaud. It provides differential transmit capability to
the bus and differential receiver capability to the CAN
protocol controller. It is fully compatible to the “ISO 11898-
2” standard.
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.
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.
The pins CANH and CANL are protected from automotive
electrical transients (according to “ISO 7637”; see Fig.4).
Control pin S allows two operating modes to be selected:
high-speed mode or silent mode.
Data Sheet
The high-speed mode is the normal operating mode and is
selected by connecting pin S to ground. It is the default
mode if pin S is not connected.
In the silent mode, the transmitter is disabled. All other IC
functions continue to operate. The silent mode is selected
by connecting pin S to VCC and can be used to prevent
network communication from being blocked, due to a CAN
controller which is out of control.
A ‘TXD dominant time-out’ timer circuit prevents the bus
lines 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, the transmitter is
disabled, driving the bus into a recessive state. The timer is
reset by a positive edge on pin TXD.
Table 1: Function table of the CAN transceiver; X = don’t care
VCC
4.75 to 5.25V
4.75 to 5.25V
4.75 to 5.25V
VCC<PORL
(POR-level;
not powered)
PORL <VCC < 4.75V
TXD
0
X
1 (or floating)
S
0 (or floating)
1
X
CANH
HIGH
0.5VCC
0.5VCC
CANL
LOW
0.5VCC
0.5VCC
BUS State
Dominant
Recessive
Recessive
RXD
0
1
1
X
>2V
X
X
0V < VCANH <VCC
0V < VCANH <VCC
0V <VCANL <VCC
0V <VCANL <VCC
Recessive
Recessive
1
1
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