TH8055 Datasheet, PDF (3/15 Pages) Micro Electronics – Single Wire CAN Transceiver

TH8055
Single Wire CAN Transceiver
Functional Description
TxD Input Pin - Logic command to transmit on the single wire CAN bus as follows:
TxD Polarity
TxD = logic 1 (or floating) on this pin produce an
undriven or recessive bus state (low bus
voltage)
TxD = logic 0 on this pin produce either a bus
normal or a bus high voltage dominant state
depending on the transceiver mode state (high
bus voltage)
If the TxD pin is driven to a logic low state while the
sleep mode (Mode0=0 and Mode1=0) is activated,
the transceiver not drive the CANH pin to the
dominant state.
The transceiver provides an internal pull up current
on the TxD pin which will cause the transmitter to
default to the bus recessive state when TxD is not
driven.
TxD input signals are standard CMOS logic levels.
Timeout Feature
In case of a faulty blocked dominant TxD input
signal the CANH output is switched off automatically
after the specified TxD timeout reaction time to
prevent a dominant bus.
The transmission is continued by next TxD L to H
transition without delay.
Mode 0 and Mode 1 pins - are used to select transceiver operating modes:
The transceiver provides a weak internal pull down
current on each of these pins which causes the
transceiver to default to sleep mode when they are
not driven. The mode input signals are standard
CMOS logic level.
M0
M1 Mode
L
L Sleep mode
H
L High speed mode
L
H Wake up
H
H Normal mode
Sleep Mode
Transceiver is in low power state, waiting for wake
up via high voltage signal or by mode pins change to
any state other than 0,0. In this state, the CANH pin
is not in the dominant state regardless of the state of
the TxD pin.
High Speed Mode
This mode allows high speed download with bitrates
up to 100Kbit/s. The output waveshaping circuit is
disabled in this mode. Bus transmitter drive circuits
for those nodes which are required to communicate
in high speed mode are able to drive reduced bus
resistance in this mode (see Table Static
Characteristics). High speed communications shall
utilize the normal mode signal voltage levels as
specified in Static Characteristics.
Wake Up Mode
This bus includes a selective node awake capability,
which allows normal communication to take place
among some nodes while leaving the other nodes in
an undisturbed sleep state. This is accomplished by
controlling the signal voltages such that all nodes
must wake up when they receive a higher voltage
message signal waveform. The communication
system communicates to the nodes information as to
which nodes are to stay operational (awake) and
which nodes are to put themselves into a non
communicating low power “sleep” state.
Communication at the lower, normal voltage levels
shall not disturb the sleeping nodes.
Normal mode
Transmission bit rate in normal communication is 33
Kbits/s. In normal transmission mode the TH8055
supports controlled waveform rise and overshoot
times. Waveform trailing edge control is required to
assure that high frequency components are
minimized at the beginning of the downward voltage
slope. The remaining fall time occurs after the bus
is inactive with drivers off and is determined by the
RC time constant of the total bus load.
390108055
Rev. 1.1a
Page 3 of 15
Jan 2002