AMIS-41683_15 Datasheet, PDF (7/16 Pages) ON Semiconductor – Fault Tolerant CAN Transceiver

AMIS−41682, AMIS−41683
• Local Wake−up: Rising or falling edge on input WAKE
(levels maintained for a certain period).
• Remote Wake−up from CAN Bus: A message with five
consecutive dominant bits.
On a wake−up request the transceiver will set the output
on Pin INH high which can be used to activate the external
supply voltage regulator. Note: Pin INH is also set similarly
as an after wake up event by V_BAT voltage being below the
battery power on flag level. (See FLAG_VBAT in Figure 5)
If V_CC is provided, the wake−up request can be read on the
ERR or RXD outputs so the external microcontroller can
wake−up the transceiver (switch to normal operating mode)
via Pins STB and EN.
In the low power modes the failure detection circuit
remains partly active to prevent increased power
consumption in the event of failures 3, 3a, 4, and 7.
The go−to−sleep−mode is only a transition mode. The Pin
INH stays active for a limited time. During this time the
circuit can still go to another low−power mode. After this
time the circuit goes to the sleep−mode. In case of a wake up
request (from BUS or WAKE Pin) during this transition
time, the wake−up request has higher priority than
go−to−sleep and INH will not be deactivated.
Behavior in Case of Missing Supplies
If V_CC is below the threshold level FLAG_V_CC, the signals
on pins STB and EN will internally be set to low-level to
provide fail safe functionality. In this way, a low-power mode
will be forced in case of missing/failing V_CC supply.
Similarly, missing/failing V_BAT supply – i.e. V_BAT being
below FLAG_V_BAT level - will lead to a fail-safe behavior of
the transceiver by forcing a low-power mode.
A forced low-power in case of missing supplies
guarantees that the transceiver will in no way disturb the
other CAN nodes when the local electronic unit looses
ground or battery connection.
EN change state
Power−On Stand−by
STB EN INH ERR RxD RTL
High Low
Act
POR−
flag
WU−
int
Vbat
EN, STB change state
Normal Mode
STB EN INH ERR RxD RTL
High High Act
Err−
flag
Rec.
out
Vcc
STB change state
STB change state
GoTo Sleep Mode
STB EN INH ERR RxD RTL
Low
High
Act
2)
WU−
int
WU−
int
Vbat
Time−out GoToSleep mode
EN, STB change state
EN change state
Standby Mode
STB EN INH ERR RxD RTL
1) Only when Vcc > POR_Vcc
Low Low
Act
WU−
int
WU−
int
Vbat
Local or Remote
Wake−up 3)
2) INH active for a time = T_GoToSleep
3) Local Wake−up through pin Wake which change state ^{Power−On}
for a time > T_wake_min
Remote Wake−up through pin CANL or CANH when
dominant for a time >TCANH_min or TCANL_min
4) Mode Change through pins STB and EN is only
possible if Vcc > POR_Vcc
Figure 5. Low Power Modes
Sleep Mode
STB EN INH ERR RxD RTL
Low Low
Hz
WU−
int 1)
WU−
int 1)
Vbat
Mode Change 4)
Power−On
After power−on (V_BAT switched on) the signal on Pin INH
will become high and an internal power−on flag will be set.
This flag can be read in the power−on standby mode via pin
ERR (STB = 1; EN = 0) and will be reset by entering the
normal operating mode.
Protections
A current limiting circuit protects the transmitter output
stages against short circuit to positive and negative battery
voltage. If the junction temperature exceeds a maximum
value, the transmitter output stages are disabled and flagged
on the ERR pin. Because the transmitter is responsible for
the major part of the power dissipation, this will result in
reduced power dissipation and hence a lower chip
temperature. All other parts of the IC will remain operating.
The Pins CANH and CANL are protected against
electrical transients that may occur in an automotive
environment.
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