3
ATA6661/ATA6662 [APPLICATION NOTE]
4968D–AUTO–06/15
1.
Hardware Description
In the following sections only the normal operating conditions will be described. For detailed information concerning the
mentioned features, refer to the corresponding datasheet.
1.1
Power Supply (VBAT, +5V and GND)
The development board requires an external 5.7V to 18V DC power supply between the terminals VBAT and GND. The
input circuit is protected against inverse-polarity with the protection diode D1, so that there is normally a difference between
the VBAT and VS level of approximately 0.7V.
The DC voltage at pin +5V is only needed when the pull-up resistor for the pin RXD is to be activated.
1.2
LIN Interface (LIN, TXD and RXD)
1.2.1
Bus Pin (LIN)
A low-side driver with internal current limitation, thermal shutdown, and an internal pull-up resistor in compliance with LIN
spec 2.0 is implemented. LIN receiver thresholds are compatible to the LIN protocol specification.
On the board at the LIN pin there is a 220-pF capacitor to ground. Additionally, the two extra components (diode D2
(LL4148) in series with resistor R3 (1 k
)) necessary to use the development board for a LIN master application have
designated placeholders for convenient mounting.
1.2.2
Input Pin (TXD)
This pin is the microcontroller interface to control the state of the LIN output. TXD must be pulled to ground in order to have
the LIN bus low. If TXD is high, the LIN output transistor is turned off and the bus is in the recessive state, pulled up by the
internal resistor. If TXD is low, the LIN output transistor is turned on and the bus is in the dominant state. An internal timer
prevents the bus line from being driven permanently in the dominant state. If TXD is forced to low longer than t
DOM
> 20 ms,
the LIN bus driver is switched to the recessive state.
1.2.3
Output Pin (RXD)
This pin reports the state of the LIN bus to the microcontroller. LIN high (recessive state) is reported by a high level at RXD,
LIN low (dominant state) is reported by a low level at RXD. The output is short-circuit protected.
Please note that the Atmel
®
ATA6661/ATA6662 has to be in normal mode in order to have the communication via LIN
enabled.
1.3
System Control (EN, INH and WAKE)
1.3.1
Enable Pin (EN)
This pin controls the operation mode of the interface. If EN = 1 the interface is in normal mode, with transmission paths from
TXD to LIN and from LIN to RXD both active. If EN = 0 the device is switched to sleep mode and no transmission is possible.
1.3.2
Inhibit Pin (INH)
This pin is used to control an external switchable voltage regulator having an inhibit input. The inhibit pin is a high-side switch
structure connected to VS. If the device is in normal mode, the inhibit high-side switch is turned on and the external voltage
regulator is activated. When the device is in sleep mode, the inhibit switch is turned off and the external voltage regulator will
be disabled.
1.3.3
Wake Pin (WAKE)
This pin is a high voltage input used to wake the device up from sleep mode. It is usually connected to an external switch in
order to generate a local wake-up.
If no local wake-up is needed in the application, the WAKE pin should be connected directly to the VS pin.
