8

9146D–AUTO–09/10

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

that no transient creates a wake-up. The device then switches to fail-safe mode. Pin INH is

activated (switches to V

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 > 6 µs 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 5k

Ω) 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

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

High

Low

On state

High

Regulator wake-up time delay

Wake pin

INH

EN

TXD

RXD

Voltage

regulator