Rainbow Electronics ATA6670 - Manual (Page 7)

7
9204C–AUTO–09/11
Atmel ATA6670 [Preliminary]
3.12 Remote Wake-up via Dominant Bus State
A voltage lower than the LIN pre-wake detection VLINL at pin LIN activates the internal LIN
receiver and starts the wake-up detection timer.
A falling edge at pin LIN, followed by a dominant bus level V
BUSdom
maintained for a certain
period of time (> t
BUS
) and a rising edge at pin LIN results in a remote wake-up request. The
transceiver switches to fail-safe mode, at transceiver 2 the INH2 output is activated (switches
to VS2) and the internal termination resistor is switched on. The remote wake-up request is
indicated by a low level at pin RXD to interrupt the microcontroller (see
Figure 3-2 ).
Figure 3-2. LIN Wake-up Waveform Diagram
In sleep mode the device has a very low current consumption even during short-circuits or
floating conditions on the bus. A floating bus can arise if the master pull-up resistor is missing,
e.g., it is switched off when the LIN master is in sleep mode or even if the power supply of the
master node is switched off.
In order to minimize the current consumption I
VS
during voltage levels at the LIN pin below the
LIN pre-wake threshold, the receiver is activated only for a specific time t
mon
. If t
mon
elapses
while the voltage at the bus is lower than pre-wake detection low (V
LINL
) and higher than the
LIN-dominant level, the receiver is switched off again and the circuit reverts to sleep mode.
The current consumption is then the result of I
VSsleep
plus I
LINwake
. If a dominant state is rea-
ched on the bus, no wake-up will occur. Even if the voltage rises above the pre-wake detection
high (V
LINH
), the IC will stay in sleep mode (see Figure 3-3 on page 8 ).
This means the LIN bus must be above the pre-wake detection threshold V
LINH
for a few
microseconds before a new LIN wake-up is possible.
LIN B us
RXD
EN
High or flo a ting
Norm a l
Mode
EN High
Node in s leep s t a te
Low
B us w a ke- u p filtering time
(t
BU S
)