Philips AU5780A Datasheet

INTEGRATED CIRCUITS

AU5780A

SAE/J1850/VPW transceiver

Preliminary specification
Supersedes data of 1998 Feb 11

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1999 Jan 28

Philips Semiconductors Preliminary specification

AU5780ASAE/J1850/VPW transceiver

FEATURES

•Supports SAE/J1850 VPW standard for in-vehicle class B

multiplexing

•Bus speed 10.4 kbps nominal

DESCRIPTION

The AU5780A is a line transceiver being primarily intended for
in-vehicle multiplex applications. It provides interfacing between a
link controller and the physical bus wire. The device supports the
SAE/J1850 VPWM standard with a nominal bus speed of 10.4 kbps.

•Drive capability 32 bus nodes

•Low RFI due to output waveshaping with adjustable slew rate

PIN CONFIGURATION

•Direct battery operation with protection against +50V load dump,

jump start and reverse battery

•Bus terminals proof against automotive transients up to

–200V/+200V

BATT

1

8

GND

•Thermal overload protection

•Very low bus idle power consumption

•Diagnostic loop-back mode

R/F

2

TX

AU5780A

3

7

6

BUS_OUT

/LB

•4X mode (41.6 kbps) reception capability

•ESD protected to 9 KV on bus and battery pins

•8-pin SOIC

QUICK REFERENCE DA TA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

V

BATT.op

T

A

V

BATT.ld

I

BATT.lp

V

B

V

BOH

–I

BO.LIM

V

BI

t

bo

tr, t

f

Operating supply voltage 6 12 24 V
Operating ambient temperature –40 +125 °C
Battery voltage load dump; 1s +50 V
Bus idle supply current V
Bus voltage 0 < V
Bus output voltage 300Ω < RL < 1.6kΩ 7.3 8.0 V
Bus output source current 0V < VBO < +8.5V 27 50 mA
Bus input threshold 3.65 4.1 V
Delay TX to BUS_OUT, normal battery Measured at 3.875V 13 21 µs
BUS_OUT transition times, rise and fall,

normal battery

=12V 220 µA

BATT

< 24V –20 +20 V

BATT

Measured between

1.5 V and (V
9 < V
t

tested at an additional bus

r

load of R
C

LOAD

BATT

< 16 V,

BATT

LOAD

= 22000 pF

RX

– 2.75 V),

= 400 W and

4

11 18 µs

SO8

5

BUS_IN

SL01207

ORDERING INFORMATION

DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG #

SO8: 8-pin plastic small outline package; Packed in tubes –40 to +125°C AU5780AD SOT96-1
SO8: 8-pin plastic small outline package; Packed on tape & reel –40 to +125°C AU5780AD–T SOT96-1

1999 Jan 28

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Philips Semiconductors Preliminary specification

AU5780ASAE/J1850/VPW transceiver

BLOCK DIAGRAM

BATTERY (+12V)

BATT
1

LOW–POWER

TIMER

TX

2

Rs

Vcc

Rd

R/F

/LB

RX

3

6

4

TX–

BUFFER

INPUT

BUFFER

VOLTAGE

REFERENCE

VOLTAGE

REFERENCE

TEMP.

PROTECTION

OUTPUT
BUFFER

INPUT

FILTER

7

5

BUS_OUT

Rb

Rf

BUS_IN

1999 Jan 28

AU5780

8

GND

SL01208

3

Philips Semiconductors Preliminary specification

AU5780ASAE/J1850/VPW transceiver

PIN DESCRIPTION

SYMBOL PIN DESCRIPTION

BATT 1 Battery supply input (12V nom.)
TX 2 Transmit data input; low: transmitter passive; high: transmitter active
R/F 3 Rise/fall slew rate set input
RX 4 Receive data output; low: active bus condition detected; float/high: passive bus condition detected
BUS_IN 5 Bus line receive input
/LB 6 Loop-back test mode control input; low: loop-back mode; high: normal communication mode
BUS_OUT 7 Bus line transmit output
GND 8 Ground

FUNCTIONAL DESCRIPTION

The AU5780A is an integrated line transceiver IC that interfaces an
SAE/J1850 protocol controller IC to the vehicle’s multiplexed bus
line. It is primarily intended for automotive “Class B” multiplexing
applications in passenger cars using VPW (Variable Pulse Width)
modulated signals with a nominal bit rate of 10.4 kbps. The
AU5780A also receives messages in the so-called 4X mode where
data is transmitted with a typical bit rate of 41.6 kbps. The device
provides transmit and receive capability as well as protection to a
J1850 electronic module.

A J1850 link controller feeds the transmit data stream to the
transceiver’s TX input. The AU5780A transceiver waveshapes the
TX data input signal with controlled rise & fall slew rates and
rounded shape. The bus output signal is transmitted with both
voltage and current control. The BUS_IN input is connected to the
physical bus line via an external resistor. The external resistor and
an internal capacitance provides filtering against RF bus noise. The
incoming signal is output at the RX pin being connected to the
J1850 link controller.

If the TX input is idle for a certain time, then the AU5780A enters a
low-power mode. This mode is dedicated to help meet ignition-off
current draw requirements. The BUS_IN input comparator is kept
alive in the low-power mode. Normal power mode will be entered
again upon detection of activity, i.e., rising edge at the TX input. The
device is able to receive and transmit a valid J1850 message when
initially in low-power mode.

The AU5780A features special robustness at its BATT and
BUS_OUT pins hence the device is well suited for applications in

the automotive environment. Specifically, the BATT input is
protected against 50V load dump, jump start and reverse battery
condition. The BUS_OUT output is protected against wiring fault
conditions, e.g., short circuit to battery voltage as well as typical
automotive transients (i.e., –200V / +200V). In addition, an
overtemperature shutdown function with hysteresis is incorporated
which protects the device under system fault conditions. The chip
temperature is sensed at the bus drive transistor in the output buffer.
In case of the chip temperature reaching the trip point, the AU5780A
will latch-off the transceiver function. The device is reset on the first
rising edge on the TX input after a small decrease of the chip
temperature.

The AU5780A also provides a loop-back mode for diagnostic
purpose. If the /LB pin is open circuit or pulled low, then TX signal is
internally looped back to the RX output independent of the signals
on the bus. In this mode the electronic module is disconnected from
the bus, i.e., the TX signal is not output to the physical bus line. In
this mode, it can be used, e.g., for self-test purpose.

The AU5780A is an enhanced successor of the AU5780. The
AU5780A provides improved wave shaping when exiting the low
power standby mode for reduced EMI. Several parameters that
were formerly only characterized to the maximum normal operating
supply of 16 volts, have now been characterized to 24 volt supplies.
These parameters which are tested and guaranteed to 24 volts are
identified with appropriate test conditions in the “conditions” columns
of the Characteristics tables, otherwise the conditions at the top of
the characteristic table applies to all parameters.

1999 Jan 28

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