AMIS-42670 Datasheet, PDF (4/12 Pages) AMI SEMICONDUCTOR – High-Speed CAN Transceiver

AMIS-42670 High-Speed CAN Transceiver
For Long Networks
Data Sheet
7.0 Functional Description
7.1 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 3: Functional table of AMIS-42670; X = don’t care
VCC
pin TxD
pin S
4.75 to 5.25.V
4.75 to 5.25.V
4.75 to 5.25.V
VCC<PORL (unpowered)
PORL<VCC<4.75V
0
X
1 (or floating)
X
>2V
0 (or floating)
1
X
X
X
pin CANH
High
VCC/2
VCC/2
0V<CANH<VCC
0V<CANH<VCC
pin CANL
Low
VCC/2
VCC/2
0V<CANL<VCC
0V<CANL<VCC
Bus state
Dominant
Recessive
Recessive
Recessive
Recessive
pin RxD
0
1
1
1
1
7.1.1. 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.
7.1.2. 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
VCC and can be used to prevent network communication from being blocked, due to a CAN controller which is out of control.
7.2 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 necessary when a bus line short-circuits.
7.3 High Communication Speed Range
The transceiver is primarily intended for industrial applications. It allows very low baud rates needed for long bus length applications.
But also high speed communication is possible up to 1Mbit/s.
7.4 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 dissipation increases during this fault condition.
The pins CANH and CANL are protected from automotive electrical transients (according to “ISO 7637”; see Figure 4). Pin TxD is
pulled high internally should the input become disconnected.
AMI Semiconductor – October 07, Rev. 1.0
4
www.amis.com Specifications subject to change without notice