ATA6621 Ver la hoja de datos (PDF) - Atmel Corporation

Número de pieza

componentes Descripción

Fabricante

ATA6621

LIN Transceiver with 5V Regulator and Watchdog

Atmel Corporation 

ATA6621

3.14 Wake-up Scenarios from Silent or Sleep Mode

3.14.1

3.14.2

3.14.3

Remote Wake-up via Dominant Bus State

A falling edge at pin LIN followed by a dominant bus level maintained for a certain time period

(TBUS) results in a remote wake-up request. The device switches to Pre Normal Mode. The VCC

voltage regulator is activated, and the internal slave termination resistor is switched on. The

remote wake-up request is indicated by a low level at pin RXD to generate an interrupt in the

microcontroller. The watchdog needs a trigger signal from PTRIG or NTRIG within the lead time

tD to avoid resets at NRES. (Figure 3-2 on page 7)

Local Wake-up via Pin Wake

A falling edge at pin WAKE followed by a low level maintained for a certain time period (TWAKE)

results in a local wake-up request. The extra long wake-up time (TWAKE) ensures that no tran-

sients as defined in ISO7637 create a wake-up. The device switches to Pre Normal Mode. The

internal slave termination resistor is switched on. The local wake-up request is indicated by a low

level at pin RXD to generate an interrupt in the microcontroller. The watchdog needs a trigger

signal from PTRIG or NTRIG within the lead time tD to avoid resets at NRES.

Wake-up Source Recognition

The device can distinguish between a local wake-up request (pin WAKE) and a remote wake-up

request (dominant LIN bus state). The wake-up source can be read on pin TXD in Pre Normal

Mode. A high level indicates a remote wake-up request (weak pull down at pin TXD) and a low

level indicates a local wake-up request (strong pull down at pin TXD). The wake-up request flag

(signalled on pin RXD) as well as the wake-up source flag (signalled on pin TXD) are reset

immediately, if the microcontroller sets pin EN to high (Figure 3-2 on page 7 and Figure 3-3 on

page 8).

3.15

Fail-safe Features

• During a short circuit at LIN, the output limits the output current to IBUS_LIM. Due to the power

dissipation, the chip temperature exceeds TLINoff and the LIN output is switched off. The chip

cools down and after a hysteresis of Thys, switches the output on again. During LIN

overtemperature switch-off, the VCC regulator works independently.

• The reverse current at pin LIN is very low (< 3 µA) during loss of VBAT or GND. This is optimal

behavior for bus systems where some slave modes are supplied from battery or ignition.

• During a short circuit at VCC, the output limits the output current to IVCCn. Because of

undervoltage, NRES switches to low and sends a reset to the microcontroller. The IC

switches into Pre Normal Mode. If the chip temperature exceeds the value TVCCoff, the VCC

output switches off. The chip cools down and after a hysteresis of Thys, switches the output on

again. Because of Pre Normal Mode, the VCC voltage will switch on again although EN is

switched off from the microcontroller. The microcontroller can start its normal operation.

• Pin EN provides a pull-down resistor to force the transceiver into recessive mode if EN is

disconnected.

• Pin RXD is connected with 5 kΩ to VCC, if VBatt is disconnected VCC is at GND level

• Pin TXD provides a pull-up resistor to force the transceiver into recessive mode if TXD is

disconnected.

• If the WD_OSC pin has a short circuit to GND or the resistor is disconnected, the watchdog

oscillator runs with a high frequency and guarantees a reset in any condition.

11

4887D–AUTO–12/06

Share Link: