33661 datasheet(13/20 Pages) MOTOROLA

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MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

33661

SYSTEM/APPLICATION INFORMATION

INTRODUCTION

The 33661 is a Physical Layer component dedicated to

automotive LIN sub-bus applications.

The 33661 features include slew rate selection for optimized

operation at 10 kbps and 20 kbps, fast baud rate for test and

programming modes, excellent radiated emission performance,

and safe behavior in case of LIN bus short-to-ground or LIN bus

leakage during low power mode.

Digital inputs are 5.0 V and 3.3 V compatible without any

external component required.

The INH output may be used to control an external voltage

regulator or to drive a LIN bus pullup resistor.

FUNCTIONAL TERMINAL DESCRIPTION

VSUP Supply Terminal

The VSUP supply terminal is the power supply terminal for the

33661.

LIN Bus Terminal

This I/O terminal represents the single-wire bus transmitter

and receiver.

TXD Input Terminal

The TXD input terminal is the MCU interface to control the

state of the LIN output. When TXD is LOW, LIN output is LOW;

when TXD is HIGH, the LIN output transistor is turned OFF. The

threshold is 3.3 V and 5.0 V compatible. The baud rate

selection (normal or slow mode) is done at device wake-up by

the state of the TXD terminal prior to a HIGH level at the EN

terminal (see Figures 5 through 10, page 10).

RXD Output Terminal

The RXD output terminal is the MCU interface, which reports

the state of the LIN bus voltage. LIN HIGH (recessive) is

reported by a high voltage on RXD; LIN LOW (dominant) is

reported by a low voltage on RXD. The RXD output structure is

a CMOS-type push-pull output stage.

The low level is fixed. The high level is dependant on the EN

voltage. If EN is set at 3.3 V, RXD VOH is 3.3 V. If EN is set at

5.0 V, RXD VOH is 5.0 V.

In the sleep mode, RXD is high impedance. When a wake-up

event is recognized from WAKE terminal or from the LIN bus

terminal, RXD is pulled LOW to report the wake-up event. An

external pullup resistor may be needed.

EN Input Terminal

The EN input terminal controls the operation mode of the

interface. If EN = 1, the interface is in normal mode, with

transmission path from TXD to LIN and from LIN to RXD both

active. The threshold is 3.3 V and 5.0 V compatible. The high

level at EN defines the VOH at RXD. The sleep mode is entered

by setting EN LOW while TXD is HIGH. Sleep mode is active

after the t1 filter time (see Figure 12, page 11).

INH Output Terminal

The INH output terminal may have two main functions. It may

be used to control an external switchable voltage regulator

having an inhibit input. The high drive capability also allows it to

drive the bus external resistor in the master node application.

This is illustrated in Figures 16 and 17, page 17.

In sleep mode, INH is turned OFF. If a voltage regulator

inhibit input is connected to INH, the regulator will be disabled.

If the master node pullup resistor is connected to INH, the

pullup resistor will be disabled from the LIN bus.

WAKE Input Terminal

The WAKE terminal is a high-voltage input used to wake up

the device from the sleep mode. WAKE is usually connected to

an external switch in the application. The typical wake thresholds

are VSUP/2.

The WAKE terminal has a special design structure and

allows wake-up from both HIGH-to-LOW or LOW-to-HIGH

transitions. When entering into sleep mode, the LIN monitors

the state of the WAKE terminal and stores it as a reference

state. The opposite state of this reference state will be the

wake-up event used by the device to enter again into normal

mode.

An internal filter is implemented (40

µs typical filtering time

delay). WAKE terminal input structure exhibits a high

impedance, with extremely low input current when voltage at

this terminal is below 14 V. When voltage at the WAKE terminal

exceeds 14 V, input current starts to sink into the device. A

serial resistor should be inserted in order to limit the input

current mainly during transient pulses. Recommended resistor

value is 33 k

Ω.

Important The WAKE terminal should not be left open. If

the wake-up function is not used, WAKE should be connected

to ground to avoid false wake-up.

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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