AMIS-42670_13 Datasheet, PDF (4/10 Pages) ON Semiconductor – High-Speed CAN Transceiver for Long Networks

AMIS−42670
FUNCTIONAL DESCRIPTION
Operating Modes
The behavior of AMIS−42670 under various conditions is
illustrated in Table 3 below. In case the device is powered,
one of two operating modes can be selected through Pin S.
Table 5. FUNCTIONAL TABLE OF AMIS−42670; x = don’t care
VCC
Pin TxD
Pin S
Pin CANH
Pin CANL
Bus State Pin RxD
4.75 V to 5.25 V
0
0
(or Floating)
High
Low
Dominant
0
4.75 V to 5.25 V
4.75 V to 5.25 V
x
1
1
X
(or Floating)
V_CC/2
V_CC/2
V_CC/2
V_CC/2
Recessive
1
Recessive
1
V_CC < PORL
(Unpowered)
x
X
0 V < CANH < V_CC 0 V < CANL < V_CC
Recessive
1
PORL < V_CC < 4.75 V
>2V
X
0 V < CANH < V_CC 0 V < CANL < V_CC
Recessive
1
High−Speed Mode
If Pin S is pulled low (or left floating), the transceiver is
in its high−speed mode and is able to communicate via the
bus lines. The signals are transmitted and received to the
CAN controller via the Pins TxD and RxD. The slopes on
the bus line outputs are optimized to give extremely low
electromagnetic emissions.
IC functions continue to operate. The transmitter off−state
resets when Pin TxD goes high. The thermal protection
circuit is particularly necessary when a bus line
short−circuits.
High Communication Speed Range
The transceiver is primarily intended for industrial
applications. It allows very low baud rates needed for long
Silent Mode
In silent mode, the transmitter is disabled. All other IC
functions continue to operate. The silent mode is selected by
connecting Pin S to V_CC and can be used to prevent network
communication from being blocked, due to a CAN
controller which is out of control.
bus length applications. But also high speed communication
is possible up to 1 Mbit/s.
Fail−Safe Features
A current−limiting circuit protects the transmitter output
stage from damage caused by an accidental short−circuit to
either positive or negative supply voltage, although power
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
dissipation increases during this fault condition.
The pins CANH and CANL are protected from
automotive electrical transients (according to “ISO 7637”;
see Figure 3). Pin TxD is pulled high internally should the
input become disconnected.
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