ATA6661 データシートの表示（PDF） - Atmel Corporation

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ATA6661

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ATA6661

3. Functional Description

3.1 Supply Pin (VS)

Undervoltage detection is implemented to disable transmission if VS is falling to a value below

5V to avoid false bus messages. After switching on VS the IC switches to pre-normal mode and

INHIBIT is switched on. The supply current in sleep mode is typically 10 µA.

3.2 Ground Pin (GND)

The ATA6661 is neutral on the LIN pin in case of a GND disconnection. It is able to handle a

ground shift up to 3V for VS > 9V.

3.3 Bus Pin (LIN)

A low-side driver with internal current limitation and thermal shutdown as well as an internal

pull-up resistor according to LIN specification 2.0 are implemented. The voltage range is from

–27V to +60V. This pin exhibits no reverse current from the LIN bus to VS, even in case of a

GND shift or VBatt disconnection. The LIN receiver thresholds are compatible to 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 short circuit limitation. This is a self adapting

current limitation; i.e., during current limitation as the chip temperature increases so the current

reduces.

3.4 Input Pin (TXD)

This pin is the microcontroller interface to control the state of the LIN output. TXD is low to bring

LIN low. If TXD is high, the LIN output transistor is turned off. In this case, the bus is in recessive

mode via the internal pull-up resistor. The TXD pin is compatible to a 3.3V and 5V supply.

3.5 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 low longer than tdom > 6 ms, the pin

LIN will be switched off to recessive mode. To reset this mode switch TXD to high (>10 µs)

before switching LIN to dominant again.

3.6 Output Pin (RXD)

This pin reports to the microcontroller the state of the LIN bus. 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 to a 3.3V or 5V power supply. The AC characteristics are

defined with a pull-up resistor of 5 kΩ to 5V and a load capacitor of 20 pF. The output is short-cur-

rent protected. In unpowered mode (VS = 0V), RXD is switched off. For ESD protection a Zener

diode is implemented with VZ = 6.1V.

3

4729M–AUTO–02/09

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