Rainbow Electronics ATA6670 - Manual (Page 5)

5
9204C–AUTO–09/11
Atmel ATA6670 [Preliminary]
3.7 Output Pin (RXD)
This pin reports the state of the LIN bus to the microcontroller. LIN high (recessive) is reported
by a high level at RXD, LIN low (dominant) is reported by a low voltage at RXD. The output is
an open drain, therefore it is compatible with a 3.3V or 5V power supply. The AC characteri-
stics are defined with a pull-up resistor of 5k
Ω
to 5V and a load capacitor of 20pF. The output
is short current protected. In unpowered mode (V
S
= 0V) RXD is switched off. For ESD protec-
tion a Zener diode is integrated with V
Z
= 6.1V.
3.8 Enable Input Pin (EN)
This pin controls the operation mode of the LIN transceiver. If EN = 1, the LIN transceiver is in
normal mode, with the transmission path from TXD to LIN and from LIN to RXD both active. At
a falling edge on EN, while TXD is already set to high, the device is switched to sleep mode
and no transmission is possible. In sleep mode, the LIN bus pin is connected to V
S
with a
weak pull-up current source. The device can transmit only after being woken up. During sleep
mode the device is still supplied from the battery voltage. The supply current is typically 10µA.
The pin EN provides a pull-down resistor in order to force the transceiver into sleep mode in
case the pin is disconnected.
3.9 WAKE-up Input Pin (WAKE2, Only Available at Transceiver 2)
This pin is a high-voltage input used to wake up the transceiver 2 from sleep mode. It is usu-
ally connected to an external transistor or a switch to generate a local wake-up. A pull-up
current source with typically –10µA is implemented as well as a debounce timer with a typical
debounce time of 70µs.
Even if the WAKE2 pin is pulled to GND, it is possible to switch the transceiver 2 into sleep
mode.
If a local wake-up is not needed in the application, pin WAKE2 can be connected directly to pin
VS2.
3.10 INH Output Pin (INH2, only available at Transceiver 2)
This pin is used to control an external load or to switch the LIN master pull-up resistor on/off at
pin LIN2. The inhibit pin provides an internal switch towards VS2 which is protected by tem-
perature monitoring. If transceiver 2 is in normal or fail-safe mode, the inhibit high-side switch
is turned on. When the transceiver 2 is in sleep mode, the inhibit switch is turned off, thus dis-
abling the connected external devices.
A wake-up event on LIN2 or at pin WAKE2 puts the transceiver 2 into fail-safe mode and as a
result the INH2 switches to the VS2 level. After a system power-up (VS2 rises from zero), the
pin INH2 switches automatically to the VS2 level.