33661 datasheet(12/21 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33661

FUNCTIONAL DESCRIPTION

INTRODUCTION

FUNCTIONAL DESCRIPTION

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 PIN DESCRIPTION

POWER SUPPLY PIN (VSUP)

The VSUP supply pin is the power supply pin for the

33661. The pin is connected to a battery through a serial

diode for reverse battery protection. The DC operating

voltage is from 7.0 V to 27 V. This pin sustains standard

automotive voltage conditions such as 27 V DC during jump-

start conditions and 40 V during load dump. Supply current in

the Sleep mode is typically 8.0

µA.

GROUND PIN (GND)

In case of a ground disconnection at the module level, the

33661 does not have significant current consumption on the

LIN bus pin when in the recessive state. (Less than 100 µA is

sourced from LIN bus pin, which creates 100 mV drop

voltage from the 1.0 k

Ω LIN bus pullup resistor.)

LIN BUS PIN (LIN)

This I/O pin represents the single-wire bus transmitter and

receiver.

Transmitter Characteristics

The LIN driver is a low-side MOSFET with internal

overcurrent thermal shutdown. An internal pullup resistor with

a serial diode structure is integrated so no external pullup

components are required for the application in a slave node.

An additional pullup resistor of 1.0 k

Ω must be added when

the device is used in the master node.

Voltage can go from -18 V to 40 V without current other

than the pullup resistance. The LIN pin exhibits no reverse

current from the LIN bus line to VSUP, even in the event of

GND shift or VPWR disconnection.

The transmitter has two slew rate selections: 20 kbps

(normal slew rate) and 10 kbps (slow slew rate). The slow

slew rate can be used to improve radiated emissions.

Receiver Characteristics

The receiver thresholds are ratiometric with the device

supply pin.

DATA INPUT PIN (TXD)

The TXD input pin 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 pin prior to a HIGH level at the EN pin

(see Figures 7 through 12, pp. 10–11).

DATA OUTPUT PIN (RXD)

The RXD output pin 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 pin or from the LIN bus

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

external pullup resistor may be needed.

ENABLE INPUT PIN (EN)

The EN input pin 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 tSD filter time (see Figure 14, 11).

INHIBIT OUTPUT PIN (INH)

The INH output pin 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 18 and 19, 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.

33661 Datasheet(PDF) 12 Page - Freescale Semiconductor, Inc

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