4

9146D–AUTO–09/10

Atmel ATA6663/ATA6664

3.7

Output Pin (RXD)

This pin forwards information on the state of the LIN bus to the microcontroller. LIN high

(recessive) is indicated 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 to a 3.3V or 5V power supply.

The AC characteristics are defined by 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

off. For ESD protection a Zener diode with V

3.8

Enable Input Pin (EN)

This pin controls the operation mode of the device. If EN = 1, the device 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 switches to sleep mode and transmission

is not possible. In sleep mode, the LIN bus pin is connected to V

source. The device can transmit only after being woken up (see Section 3.9, “Inhibit Output

Pin (INH)” ).

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

Inhibit Output Pin (INH)

This pin is used to control an external voltage regulator or to switch on/off the LIN Master

pull-up resistor in case the device is used in a Master node. The inhibit pin provides an internal

switch towards pin V

or fail-safe mode, the inhibit high-side switch is turned on. When the device is in sleep mode,

the inhibit switch is turned off, thus disabling the voltage regulator or other connected external

devices.

A wake-up event on the LIN bus or at pin WAKE will switch the INH pin to the V

system power-up (V

3.10

Wake-up Input Pin (WAKE)

This pin is a high-voltage input used to wake-up the device from sleep mode. It is usually

connected to an external switch in the application to generate a local wake-up. A pull-up cur-

rent source with typically –10µA is implemented. The voltage threshold for a wake-up signal is

3V below the VS voltage with an output current of typically –3µA.

If a local wake-up is not needed in the application, pin WAKE can directly be connected to pin

VS.