Rainbow Electronics ATA6670 - Manual (Page 10)

10
9204C–AUTO–09/11
Atmel ATA6670 [Preliminary]
3.14 Wake- up Source Recognition (Only available at Transceiver 2)
Transceiver 2 can distinguish between a local wake-up request at pin WAKE2 and a remote
wake-up request via LIN 2. The wake-up source can be read at pin TXD in fail-safe mode. If an
external pull up resistor (typ. 5k
Ω
) has been added on pin TXD2 to the power supply of the
microcontroller, a high level indicates a remote wake-up request (weak pull down at pin
TXD2), a low level indicates a local wake-up request (strong pull down at pin TXD2).
The wake-up request flag (indicated at pin RXD2) as well as the wake-up source flag (indica-
ted at pin TXD2) are immediately reset if the microcontroller sets pin EN2 to high (see
Figure
3-5 on page 9 ).
3.15 Fail-safe Features
• During a short-circuit at LIN to V
Battery
, the output limits the output current to IBUS_LIM.
Due to the power dissipation, the chip temperature exceeds T
off
, and the LIN output is
switched off. The chip cools down and after a hysteresis of T
hys
it switches the output on
again.
• During a short-circuit from LIN to GND the transceiver can be switched into sleep mode
and even in this case the current consumption is lower than 45µA. If the short-circuit
disappears, the transceiver starts with a remote wake-up.
• If a transceiver is in sleep mode and a floating condition occurs on the bus, the transceiver
automatically switches back to sleep mode, thus decreasing current consumption to less
than 45µA in this case.
• The reverse current is < 2µA at pin LIN during loss of V
BAT
; this is optimal behavior for bus
systems where some slave nodes are supplied from battery or ignition.
• Pin EN provides a pull-down resistor to force the transceiver into sleep mode if EN is
disconnected.
• Pin RXD is set to floating if V
BAT
is disconnected.
• Pin TXD provides a pull-down resistor to provide a static low if TXD is disconnected.
• After switching the LIN transceiver into Normal Mode the TXD pin must be pulled to high
longer than 10µs in order to activate the LIN driver. This feature prevents the bus from
being driven into dominant state when the LIN transceiver is switched into Normal Mode
and TXD is low.
• The INH2 output transistor at transceiver 2 is protected by temperature monitoring