Atmel ATA6670
Dual LIN Transceiver
DATASHEET
Features
●
Operating range from 5V to 27V
●
Baud rate up to 20Kbaud
●
LIN physical layer according to LIN specification 2.0, 2.1 and SAEJ2602-2
●
Fully compatible with 3.3V and 5V devices
●
TXD dominant timeout timer
●
Normal and Sleep Mode
●
Wake-up capability via LIN bus (90µs dominant)
●
Very low standby current during Sleep Mode (10µA)
●
Bus pin is overtemperature and short-circuit protected versus GND and battery
●
LIN input current < 2µA if VBAT Is disconnected
●
Overtemperature protection
●
High EMC level
●
Interference and damage protection according to ISO/CD 7637
●
Fulfills the OEM hardware requirements for LIN in automotive applications rev. 1.1
●
Transceiver 2: additional INH high side switch output and high voltage WAKE input
Description
The Atmel
®
ATA6670 is a fully integrated Dual-LIN transceiver complying with the LIN
specification 2.0, 2.1, and SAEJ2602-2. There are two completely independent and sepa-
rated LIN transceivers integrated in one package (only the GND pins GND1 and GND2 are
internally connected). Each of them interfaces with the LIN protocol handler and the physi-
cal layer.
The two LIN transceivers are nearly identical, the only difference is an additional WAKE
input and an INH output at transceiver 2.
The device is designed to handle the low-speed data communication in vehicles, for exam-
ple, in convenience electronics. Improved slope control at the LIN driver ensures secure
data communication up to 20Kbaud. Sleep mode guarantees minimal current consumption
for each transceiver even in the case of a floating bus line or a short-circuit on the LIN bus
to GND. The Atmel ATA6670 features advanced EMI and ESD performance.
9204F–AUTO–06/12
Figure 1.
Block Diagram
14
Transceiver 1
1
RXD1
Receiver
VS1
-
+
13
Filter
LIN1
Wake up bus
timer
3
TXD1
TXD
Time-Out
Timer
Slew rate control
Short circuit
and over-
temperature
protection
Control unit
Sleep mode
2
EN1
10
12
GND1
Transceiver 2
4
RXD2
Receiver
VS2
-
+
9
Filter
LIN2
Wake up bus
timer
7
TXD2
TXD
Time-Out
Timer
Slew rate control
Short circuit
and over-
temperature
protection
V
S
Control unit
6
WAKE2
Wake-up
Timer
Sleep mode
V
S
8
GND2
11
INH2
5
EN2
Atmel ATA6670 [DATASHEET]
9204F–AUTO–06/12
2
1.
Pin Configuration
Figure 1-1. Pinning DFN14
RXD1
EN1
TXD1
RXD2
EN2
WAKE2
TXD2
VS1
LIN1
GND1
Atmel
ATA6670
INH2
VS2
LIN2
GND2
Table 1-1.
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Pin Description
Symbol
RXD1
EN1
TXD1
RXD2
EN2
WAKE2
TXD2
GND2
LIN2
VS2
INH2
GND1
LIN1
VS1
Function
Receives data output 1 (open drain)
Enables Normal mode 1. When the input is open or low, transceiver 1 is in Sleep mode.
Transmits data input 1
Receives data output 2 (open drain)
Enables Normal mode 2. When the input is open or low, transceiver 2 is in Sleep mode.
High voltage input for local wake-up request. If not needed, connect directly to VS2
Transmits data input 2. Active low output (strong pull-down) after a local wake-up request at
transceiver 2.
Ground 2
LIN bus line 2 input/output
Battery supply 2
VS2- related high-side switch output for controlling an external load, such as a voltage divider
Ground 1
LIN bus line 1 input/output
Battery supply 1
Atmel ATA6670 [DATASHEET]
9204F–AUTO–06/12
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2.
Functional Description
The functions described in the following text apply to each LIN transceiver. Therefore, if pin LIN is stated, this applies to each of
the two receivers (LIN1 and LIN2), which work completely independently. The only internal connection is between GND1 and
GND2. The functions only available at transceiver 2 are marked accordingly.
2.1
Physical Layer Compatibility
Since the LIN physical layer is independent of higher LIN layers (e.g., the LIN protocol layer), all nodes with a LIN physical layer
according to revision 2.x can be mixed with LIN physical layer nodes, which are based on older versions (i.e., LIN 1.0, LIN 1.1,
LIN 1.2, LIN 1.3) without any restrictions.
2.2
Supply Pin (VS)
Undervoltage detection is implemented to disable transmission if VS falls to a value below 5V in order to avoid false bus
messages. After switching on VS, the corresponding transceiver switches to Fail-safe mode. The supply current for each
transceiver in Sleep mode is typically 10µA.
2.3
Ground Pin (GND)
The Atmel ATA6670 does not affect the LIN bus in case of GND disconnection. It is able to handle a ground shift up to 11.5% of
V
S
.
2.4
Bus Pin (LIN)
A low-side driver with internal current limitation and thermal shutdown and an internal pull-up resistor are implemented as
specified for LIN 2.x. The voltage range is from –27V to +40V. This pin exhibits no reverse current from the LIN bus to V
S
, even
in case of a GND shift or V
Batt
disconnection. The LIN receiver thresholds are compatible with the LIN protocol specification. The
fall time (from recessive to dominant) and the rise time (from dominant to recessive) are slope-controlled. The output has a self-
adapting short-circuit limitation; in other words, during current limitation, the current decreases in proportion to an increase in
chip temperature.
Note:
The internal pull-up resistor is only active in normal and Fail-safe mode.
2.5
Input/Output Pin (TXD)
In Normal mode the TXD pin is the microcontroller interface to control the state of the LIN output. TXD must be at low level in
order to have a low LIN bus. If TXD is high, the LIN output transistor is turned off and the bus is in recessive state. The TXD pin
is compatible with both a 3.3V and 5V supply.
Only for the LIN transceiver 2: The TXD 2 pin is used in Fail-safe mode as an output in order to signal the wake-up source (see
Section 2.14 “Wake- up Source Recognition (Only available at Transceiver 2)” on page 9).
The TXD output is current limited to
< 8mA.
2.6
TXD Dominant Time-out Function
The TXD input has an internal pull-down resistor. An internal timer prevents the bus line from being driven permanently in
dominant state. If TXD is forced to low longer than t
DOM
> 70ms, the LIN pin is switched off (recessive mode). To reset this
mode, switch TXD to high (> 10µs) before switching LIN to dominant again.
2.7
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 characteristics are defined with a pull-up resistor of 5kΩ 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 protection a Zener diode is integrated with
V
Z
= 6.1V.
Atmel ATA6670 [DATASHEET]
9204F–AUTO–06/12
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2.8
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.
2.9
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 usually 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 35µs.
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.
2.10
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 temperature 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 disabling 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.
2.11
Operation Modes
1.
2.
Normal mode
This is the normal transmitting and receiving mode. All features are available.
Sleep mode
In this mode the transmission path is disabled and the device is in low power mode. Supply current from V
Batt
is typi-
cally 10µA. A wake-up signal (either from the LIN bus or the WAKE2 input) is detected and switches the
corresponding transceiver to Fail-safe mode. If EN then switches to high, Normal mode is activated. Input debounce
timers at pin WAKE2 (t
WAKE
), LIN (t
BUS
) and EN (t
sleep,tnom
) prevent undesirable wake-up events due to automotive
transients or EMI. The internal termination between pin LIN and pin VS is disabled. Only a weak pull-up current (typi-
cal 10µA) between pin LIN and pin VS is present. Sleep mode can be activated independently of the current level on
pin LIN.
Fail-safe mode
At system power-up or after a wake-up event, the transceiver automatically switches to Fail-safe mode. When VS2
exceeds 5V, the transceiver 2 switches the INH2 pin to the VS2 level. LIN communication is switched off. The micro-
controller of the application then confirms Normal mode by setting the EN pin to high.
3.
Atmel ATA6670 [DATASHEET]
9204F–AUTO–06/12
5
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