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ATA6621N

LIN Transceiver with 5V Regulator and Watchdog

Atmel Corporation 

ATA6621N

3.7 Bus Pin (LIN)

A low side driver with internal current limitation and thermal shutdown, and an internal pull-up

resistor in compliance with LIN specification 2.0 is implemented. This is a self-adapting current

limitation; that is, during current limitation, as the chip temperature increases, the current

decreases. The allowed voltage range is between –40V and +60V. Reverse currents from the

LIN bus to VS are suppressed, even in case of ground shifts or battery disconnection. LIN

receiver thresholds are compatible to the LIN protocol specification. The fall time from recessive

bus state to dominant, and the rise time from dominant bus state to recessive are slope

controlled.

3.8 Input/Output 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.

3.9 TXD Dominant Time-out Function

The TXD input has an internal pull-up resistor. An internal timer prevents the bus line from being

driven permanently in the dominant state. If TXD is forced to low longer than tDOM > 6 ms, the

LIN bus driver is switched to the recessive state. To reset this dominant time-out mode, TXD

must be switched to high (> 10 µs) before normal data transmission can be started.

3.10

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 has an internal pull-up structure with typically 5 kΩ to VCC. The AC characteristics can be

defined with an external load capacitor of 20 pF.

The output is short-circuit protected. In Unpowered mode (that is, VS = 0V), RXD is switched off.

3.11

Enable Input Pin (EN)

This pin controls the operation mode of the interface. If EN is high, the interface is in Normal

mode, with transmission paths from TXD to LIN and from LIN to RXD both being active. The VCC

voltage regulator is operating with 5V ±2%/50 mA output capability.

If EN is switched to low while TXD is still high, the device is forced to Silent mode. No data trans-

mission is then possible and the current consumption is reduced to IVS = 50 µA. The current

capability of the VCC regulator is also 50 mA, but the VCC tolerance is between 4.65V and 5.35V.

If EN is switched to low while TXD is low, the device is forced to Sleep mode. No data transmis-

sion is possible and the voltage regulator is switched off.

3.12

Wake Input Pin (WAKE)

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

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

source with typically 10 µA is implemented.

If you don’t need a local wake-up in your application, connect pin WAKE directly to pin VS.

5

4887I–AUTO–09/09

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