Rainbow Electronics ATA6670 User Manual

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

Dual LIN Transceiver

Atmel ATA6670

1. 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 separated 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 physical 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 example, in convenience electronics. Improved slope control at the LIN bus ensures secure data communication of up to 20Kbaud with an RC oscillator for protocol handling. 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.

Preliminary

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Figure 1-1. Block Diagram

Receiver

Wake up bus

timer

Slew rate control

Control unit

Filter

Short circuit and over-

temperature protection

TXD

Time-Out

Timer

Sleep mode

Receiver

RXD2

RXD1

TXD2

GND2WAKE2

EN2

Transceiver 2

Transceiver 1

Wake up bus

timer

Slew rate control

Control unit

Filter

Short circuit and over-

temperature protection

TXD

Time-Out

Timer

Wake-up

Timer

Sleep mode

TXD1

EN1

6 8

GND1

LIN2

LIN1

VS2

VS1

INH2

Atmel ATA6670 [Preliminary]

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2. Pin Configuration

Figure 2-1. Pinning DFN14

Atmel ATA6670 [Preliminary]

RXD1

EN1

TXD1

RXD2

EN2

WAKE2

TXD2

Atmel

ATA6670

VS1

LIN1

GND1

INH2

VS2

LIN2

GND2

Table 2-1. Pin Description

Pin Symbol Function

1 RXD1 Receives data output 1 (open drain) 2 EN1 Enables normal mode 1. When the input is open or low, transceiver 1 is in sleep mode. 3 TXD1 Transmits data input 1, active low output (strong pull-down) after a local wake-up request 4 RXD2 Receives data output 2 (open drain) 5 EN2 Enables normal mode 2. When the input is open or low, transceiver 2 is in sleep mode. 6 WAKE2 High voltage input for local wake-up request. If not needed, connect directly to VS2 7 TXD2 Transmits data input 2, active low output (strong pull-down) after a local wake-up request 8 GND2 Ground 2

9 LIN2 LIN bus line 2 input/output 10 VS2 Battery supply 2 11 INH2 VS2- related high-side switch output for controlling an external load, such as a voltage divider 12 GND1 Ground 1 13 LIN1 LIN bus line 1 input/output 14 VS1 Battery supply 1

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3. 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.

3.1 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.

3.2 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.

3.3 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

3.4 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 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.

3.5 Input/ Pin (TXD)

In normal mode the TXD pin is the microcontroller interface to control the state of the LIN output. TXD must be at the 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.

3.6 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 the LIN pin is switched off (recessive mode). To reset this mode, switch TXD to high (> 10µs) before switching LIN to dominant again.

, even in case of a GND shift or V

> 40ms,

DOM

Batt

Atmel ATA6670 [Preliminary]

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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 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 tion a Zener diode is integrated with V

=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 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 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 70µs.

= 0V) RXD is switched off. For ESD protec-

with a

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 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.

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3.11 Operation Modes

a: Power-up (VS > 3V) b: V

< 5V

c: Bus wake-up event

(only Transceiver 2)

d: Wake-up from wake switch

EN = 1

and not b

c or d

EN = 0

EN = 1

Fail-Safe Mode

Power-up

Communication: OFF

RXD: see table of Modes

Tr ansceiver 2: INH2 switch ON if VS2 > 5V

Sleep Mode

Communication: OFF

Tr ansceiver 2: INH2 switch OFF

Normal Mode

Communication: ON

Tr ansceiver 2: INH2 switch ON

Local wake-up event

Go to sleep command

1. Normal mode This is the normal transmitting and receiving mode. All features are available.

2. Sleep mode In this mode the transmission path is disabled and the device is in low power mode. Supply current from V

is typically 10µA. A wake-up signal (either from the LIN bus

Batt

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

) and EN (t

BUS

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 (typical 10µA) between pin LIN and pin VS is present. Sleep mode can be activated independently of the current level on pin LIN.

3. 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 microcontroller of the application then confirms normal mode by setting the EN pin to high.

Figure 3-1. Operating Modes

Atmel ATA6670 [Preliminary]

Table 3-1. Table of Modes

Operating Mode Transceiver RXD LIN

Fail-safe Off

Normal On LIN-depending TXD-depending

Sleep Off High-ohmic Recessive

High, except after

wake-up

Recessive

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