Rainbow Electronics ATA6625 - Manual (Page 10)

10
4957E–AUTO–10/07
ATA6623/ATA6625
5. 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
CC
regulator is
working independently.
• During a short-circuit from LIN to GND the IC can be switched into Sleep or Silent mode. If
the short-circuit disappears, the IC starts with a remote wake-up.
• The reverse current is very low < 15 µA at pin LIN during loss of V
Batt
or GND. 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
VCCn
. 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
CC
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
CC
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
tdom > 20 ms.