ATA663201 datasheet(13/36 Pages) MICROCHIP

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DS20006075D-page 13

ATA663201/03/31/54

1.6.4

INPUT/OUTPUT (TXD) (SBC ONLY)

In Normal mode, the TXD pin is the microcontroller

interface for controlling the state of the LIN output. TXD

must be pulled to ground in order to drive the LIN bus

low. If TXD is high or unconnected (internal pull-up

resistor), the LIN output transistor is turned off and the

bus is in the recessive state. If the TXD pin stays at

GND level while switching into Normal mode, it must be

pulled to high level longer than 10 µs before the LIN

driver can be activated. This feature prevents the bus

line from being accidentally driven to dominant state

after the Normal mode has been activated (also in case

of a short circuit at TXD to GND). During Fail-Safe

mode, this pin is used as output and signals the fail-

safe source.

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 > 20 ms, the LIN bus

driver is switched to the recessive state. Nevertheless,

when switching to Sleep mode, the actual level at the

TXD pin is relevant.

To reactivate the LIN bus driver, switch TXD to high

(> 10 µs).

1.6.5

GROUND PIN (GND)

The IC does not affect the LIN bus in the event of GND

disconnection. It is able to handle a ground shift of up

to 11.5% of VVS.

1.6.6

BUS PIN (LIN) (SBC ONLY)

A low-side driver with internal current limitation and

thermal shutdown as well as an internal pull-up resistor

according to LIN specification 2.x is implemented. The

voltage range is from -27V to +40V. This pin exhibits no

reverse current from the LIN bus to VS, even in the

event of a GND shift or VBat disconnection. The LIN

receiver thresholds comply with the LIN protocol

specification.

The fall time (from recessive to dominant) and the rise

time (from dominant to recessive) are slope-controlled.

During a short circuit at LIN to VBat, the output limits the

output current to IBUS_LIM. Due to the power

dissipation, the chip temperature exceeds TLINoff and

the LIN output is switched off. The chip cools down and

after a hysteresis of Thys, switches the output on again.

RXD stays on high because LIN is high. The VCC

regulator

works

independently

during

LIN

overtemperature switch-off.

During a short circuit from LIN to GND, the IC can be

switched into Sleep or Silent mode and even in this

case the current consumption is lower than 100 µA in

Sleep mode and lower than 120 µA in Silent mode. If

the short-circuit disappears, the IC starts with a remote

wake-up.

The reverse current is <2 µA at pin LIN during loss of

VBat. This is optimal behavior for bus systems where

some LIN nodes are supplied from battery or ignition.

1.6.7

SUPPLY PIN (VS)

LIN operating voltage is VVS = 5V to 28V. Undervoltage

detection is implemented to disable transmission if VVS

falls below typical 4.5V, thereby avoiding false bus

messages. After switching on VVS, the IC starts in Fail-

Safe mode and the voltage regulator is switched on.

The supply current in Sleep mode is typically 9 µA and

47 µA in Silent mode.

1.6.8

VOLTAGE REGULATOR OUTPUT

PIN (VCC)

The internal 3.3V/5V voltage regulator is capable of

driving

loads

85 mA,

supplying

the

microcontroller and other ICs on the PCB and is

protected against overload by means of current

limitation

and

overtemperature

shutdown.

Furthermore, the output voltage is monitored and

causes a reset signal at the NRES output pin if it drops

below a defined threshold VVCC_th_uv_down.

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