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TERMINAL FUNCTIONS

LIN Bus Pin

Transmit Input Pin (TXD)

Receive Output Pin (RXD)

TPIC1021

LIN Physical Interface

SLIS113 – OCTOBER 2004

Terminal Assignments

PIN NAME

PIN NO.

PIN TYPE

DESCRIPTION

RXD

1

O

RXD output (open drain) pin interface reporting state of LIN bus voltage

EN

2

I

Enable input pin

NWake

3

I

High voltage input pin for device wake up

TXD

4

I

TXD input pin interface to control state of LIN output

GND

5

I

Ground connection

LIN

6

I/O

LIN bus pin single wire transmitter and receiver

7

Supply

Device supply pin (connected to battery in series with external reverse blocking diode)

INH

8

O

Inhibit pin controls external voltage regulator with inhibit input

This I/O pin is the single-wire LIN bus transmitter and receiver.

Transmitter Characteristics

The driver is a low side transistor with internal current limitation and thermal shutdown. There is an internal

30-k

Ω pull-up resistor with a serial diode structure to V

slave mode applications. An external pull-up resistor of 1 k

Ω plus a series diode to V

device is used for master node applications.

Voltage on the LIN pin can go from -40 V to +40 V DC without any currents other than through the pull-up

The LIN thresholds and ac parameters are compatible LIN Protocol Specification Revision 2.0.

During a thermal shut down condition the driver is disabled.

Receiver Characteristics

The receiver’s characteristic thresholds are ratio-metric with the device supply pin. Typical thresholds are 50%,

with a hysteresis between 5% and 17.5% of supply.

This pin is the interface to the MCU’s LIN Protocol Controller or SCI/UART used to control the state of the LIN

output. When TXD is low, LIN output is dominant (near ground). When TXD is high, LIN output is recessive (near

battery). TXD input structure is compatible with microcontrollers with 3.3 V and 5.0 V I/O. This pin has an internal

pull-down resistor.

TXD Dominant State Timeout

If the TXD pin is inadvertently driven permanently low by a hardware or software application failure, the LIN bus

is protected by TPIC1021’s Dominant State Timeout Timer. This timer is triggered by a falling edge on the TXD

bus to return to the recessive state and communication to resume on the bus. The timer is reset by a rising edge

on TXD pin.

This pin is the interface to the MCU’s LIN Protocol Controller or SCI/UART, which reports the state of the LIN

bus voltage. LIN recessive (near battery) is represented by a high level on RXD and LIN dominant (near ground)

is represented by a low level on RXD. The RXD output structure is an open-drain output stage. This allows the

TPIC1021 to be used with 3.3 V and 5 V I/O microcontrollers. If the microcontroller’s RXD pin does not have an

integrated pull-up, an external pull-up resistor to the microcontroller I/O supply voltage is required.

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