Fail-safe features – Rainbow Electronics ATA6631 User Manual

Page 13

9165A–AUTO–11/09

ATA6629/ATA6631

Fail-safe Features

• During a short-circuit at LIN to V

Battery

, the output limits the output current to I

BUS_LIM

. Due to

the power dissipation, the chip temperature exceeds T

LINoff

and the LIN output is switched off.

The chip cools down and after a hysteresis of T

hys

, switches the output on again. RXD stays

on high because LIN is high. During LIN overtemperature switch-off, the V

regulator is

working independently.

• During a short-circuit from LIN to GND the IC can be switched into Sleep or Silent Mode and

even in this case the current consumption is lower than 45 µA in Sleep Mode and lower than
80 µA in Silent Mode. If the short-circuit disappears, the IC starts with a remote wake-up.

• Sleep or Silent Mode: During a floating condition on the bus the IC switches back to Sleep

Mode/Silent Mode automatically and thereby the current consumption is lower than
45 µA/80 µA.

• The reverse current is < 2 µA at pin LIN during loss of V

Batt

. This is optimal behavior for bus

systems where some slave nodes are supplied from battery or ignition.

• During a short circuit at VCC, the output limits the output current to I

VCClim

. Because of

undervoltage, NRES switches to low and sends a reset to the microcontroller. The IC
switches into Fail-safe Mode. If the chip temperature exceeds the value T

VCCoff

, the V

output switches off. The chip cools down and after a hysteresis of T

hys

, switches the output on

again. Because of Fail-safe Mode, the V

voltage will switch on again although EN is

switched off from the microcontroller.The microcontroller can then start with normal
operation.

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

disconnected.

• Pin RXD is set floating if V

Batt

is disconnected.

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

disconnected.

• If TXD is short-circuited to GND, it is possible to switch to Sleep Mode via ENABLE after

t > tdom.