|
AMIS-30523 Datasheet, PDF (34/35 Pages) ON Semiconductor – CAN Micro-Stepping Motor Driver | |||
|
◁ |
AMISâ30523
FUNCTIONAL DESCRIPTION CAN TRANSCEIVER
Introduction
The CAN transceiver is the interface between a (CAN)
protocol controller and the physical bus. It provides
differential transmit capability to the bus and differential
receive capability to the CAN controller. Due to the wide
commonâmode voltage range of the receiver inputs, it is
able to reach outstanding levels of electroâmagnetic
susceptibility (EMS). Similarly, extremely low
electromagnetic emission (EME) is achieved by the
excellent matching of the output signals.
Additional features are the ideal passive behavior when
the supply voltage is removed; a wakeâup over bus and the
extreme low current in standâby mode.
To cope with the long bus delay the communication speed
needs to be low. The integrated transceiver allows low
transmit data rates down 10 kbit/s or lower.
Operating Modes
The CAN transceiver provides two modes of operation as
illustrated in Table 19. These modes are selectable through
pin STB
Table 19. OPERATING MODES
RXD
Mode
STB
Low
High
Normal
Low
Bus
Bus
dominant
recessive
Standby
High
Wakeâup
request
detected
No
wakeâup
request
detected
In the normal mode, 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 optimized to
give extremely low EME.
In standâby mode both the transmitter and receiver are
disabled and a very lowâpower differential receiver
monitors the bus lines for CAN bus activity. The bus lines
are terminated to ground and supply current is reduced to a
minimum, typically 10 mA. When a wakeâup request is
detected by the lowâpower differential receiver, the signal
is first filtered and then verified as a valid wake signal after
a time period of tBUS, the RxD pin is driven low by the
transceiver to inform the controller of the wakeâup request.
Split Circuit
The VSPLIT pin is operational only in normal mode. In
standby mode this pin is floating. The VSPLIT is connected
as shown in Figure 13 and its purpose is to provide a
stabilized DC voltage of 0.5 x VCC to the bus avoiding
possible steps in the commonâmode signal therefore
reducing EME. These unwanted steps could be caused by an
unâpowered node on the network with excessive leakage
current from the bus that shifts the recessive voltage from its
nominal 0.5 x VCC voltage.
Wakeâup
Once a valid wakeâup (dominant state longer than tBUS)
has been received during the standby mode the RxD pin is
driven low
OverâTemperature 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 offâstate
resets when pin TxD goes high. The thermal protection
circuit is particularly needed 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
bus length applications. But also high speed communication
is possible up to 1 Mbit/s.
Fail Safe Features
A currentâlimiting 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 7). Pins TxD and STB are pulled high internally
should the input become disconnected. Pins TxD, STB and
RxD will be floating, preventing reverse supply should the
VCC supply be removed.
DEVICE ORDERING INFORMATION
Part Number
Temperature
Range
Peak
Current
Package Type
Shippingâ
AMIS30523C5231RG
â40°C â 125°C
1600 mA
QFNâ52
(PbâFree)
Tape & Reel
AMIS30523C5231G
â40°C â 125°C
1600 mA
QFNâ52
(PbâFree)
Tube
â For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
http://onsemi.com
34
|
▷ |