Rainbow Electronics ATA6630 - Manual (Page 18)

18
9117C–AUTO–10/09
ATA6628/ATA6630 [Preliminary]
5.5 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 VCC regulator
works 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 the LIN pin 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 if NRES is
connected to the microcontroller. The IC switches into Fail-safe Mode. If the chip temperature
exceeds the value T
VCCoff
, the VCC output switches off. The chip cools down and after a
hysteresis of T
hys
, switches the output on again. Because of the Fail-safe Mode, the VCC
voltage will switch on again although EN is switched off from the microcontroller. The
microcontroller can start with its normal operation.
• EN pin provides a pull-down resistor to force the transceiver into recessive mode if EN is
disconnected.
• RXD pin is set floating if V
Batt
is disconnected.
• TXD pin 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
• If the WD_OSC pin has a short-circuit to GND or the resistor is disconnected, the watchdog
runs with an internal oscillator and guarantees a reset.
• If there is no NTRIG signal and short circuit at WD_OSC the NRES switches to low after typ.
90 ms. For an open circuit (no resistor) at WD_OSC it switches to low after typ. 390 ms.