AMIS-42673 High Speed CAN Transceiver

Data Sheet

For Long Networks

7.0 Functional Description

7.1 General

The AMIS-42673 is the interface between the CAN protocol controller and the physical bus. It is intended for use in industrial and

automotive applications requiring baud rates up to 1Mbit/s. 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.

7.2 Operating Modes

AMIS-42673 only operates in high-speed mode as illustrated in Table 3.

The transceiver 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 lines outputs are optimised to give extremely low EME.

Table 3: Functional table of AMIS-42673; X = don’t care

VCC

pin TxD

pin CANH

pin CANL

Bus state

pin RxD

4.75 to 5.25.V

0

High

Low

Dominant

0

4.75 to 5.25.V

1 (or floating)

VCC/2

VCC/2

Recessive

1

VCC<PORL (unpowered)

X

0V<CANH<VCC

0V<CANL<VCC

Recessive

1

PORL<VCC<4.75V

>2V

0V<CANH<VCC

0V<CANL<VCC

Recessive

1

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 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.

7.5 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 Vcc supply is removed, pins TxD and RxD will be floating. This prevents the AMIS-42673 from being supplied by the CAN

controller through the I/O pins.

7.6 3.3V Interface

AMIS-42673 may be used to interface with 3.3V or 5V controllers by use of the V33 pin. This pin may be supplied with 3.3V or 5V to

have the corresponding digital interface voltage levels.

When the V33 pin is supplied at 2.5V, even interfacing with 2.5V CAN controllers is possible. See also Digital Output Characteristics @

V33 = 2.5V, Table 7. In this case a pull-up resistor from TxD to V33 is necessary.

4

www.amis.com

Specifications subject to change without notice