Manual

8
9146E–AUTO–03/11
Atmel ATA6663/ATA6664
3.13 Local Wake-up via Pin WAKE
A falling edge at pin WAKE, followed by a low level maintained for a certain time period
(> t
WAKE
), results in a local wake-up request. According to ISO7637, the wake-up time ensures
that no transient creates a wake-up. The device then switches to fail-safe mode. Pin INH is
activated (switches to V
S
) and the internal termination resistor is switched on. The local
wake-up request is indicated both by a low level at pin RXD to interrupt the microcontroller and
by a strong pull-down at pin TXD (see Figure 3-5). The voltage threshold for a wake-up signal
is 3V below the VS voltage with an output current of typically –3µA. Even in case of a continu-
ous low at pin WAKE it is possible to switch the IC into sleep mode via a low level at pin EN.
The IC will remain in sleep mode for an unlimited time. To generate a new wake-up at pin
WAKE, a high signal > 6µs is required. A negative edge then starts the wake-up filtering time
again.
Figure 3-5. Wake-up from Wake-up Switch
3.14 Wake-up Source Recognition
The device can distinguish between a local wake-up request (pin WAKE) and a remote
wake-up request (LIN bus). The wake-up source can be read at pin TXD in fail-safe mode. If
an external pull-up resistor (typically 5kΩ) has been added on pin TXD to the power supply of
the microcontroller, a high level indicates a remote wake-up request (weak pull-down at pin
TXD), a low level indicates a local wake-up request (strong pull-down at pin TXD).
The wake-up request flag (indicated at pin RXD) as well as the wake-up source flag (indicated
at pin TXD) are reset immediately if the microcontroller sets pin EN to high (see Figure 3-2 on
page 6 and Figure 3-5 on page 8).
Microcontroller start-up
delay time
Wake filtering time
t
WAKE
Off state
Node in sleep state
High or floating
TXD weak pull-down resistor
Low or floating
State change
TXD strong pull-down
Node in
operation
Weak
pull-down
EN High
HighLow
On state
High
Regulator wake-up time delay
Wake pin
INH
EN
TXD
RXD
Voltage
regulator