AN602 View Datasheet(PDF) - Vishay Semiconductors

Part Name

Description

MFG CO.

AN602

Driver ICs for Automotive Diagnostic Communications Meet ISO 9141 Standards

Vishay Semiconductors 

AN602

Vishay Siliconix

RXL

GND VDD VBAT

L

+

L

–

RXK

K

+

K

–

+

VBAT/2

–

VDD

Logic Circuitry

K

(See State Diagram

TX

and Truth Table)

FIGURE 3. Si9243A K- and L-Line Driver

Since the fault detection signal is not brought out, it is up to the

user to determine if a fault has occurred. One method is to monitor

the RxK and TX lines and ensure they are in phase. An exclusive

OR can also perform the fault function.

The fault condition is cleared when TX is set high.

System Anomalies

Two system anomalies in the automotive environment that the

Si924x drivers may be subjected to are Reverse Battery and

Ground Disconnect.

The Si924x drivers have an integrated diode in the VBAT line to

protect the device from reverse battery conditions. This diode will

protect the IC to reverse batteries up to –24 V.

Signal and Communication Specifications

ISO 9141 specifies different logic levels for the Receiver and

Transmitter.

Receiver Logic Levels:

Logic “0” v 0.3 * VBAT

0.7 * VBAT 3 Logic “1”

Transmitter Logic Levels:

Logic “0” v 0.2 * VBAT 0.8 *

VBAT w Logic “1”

The Vishay Siliconix drivers operate to the above specifications,

but with a slightly tighter transmission requirement: Logic “1”

minimum w 0.91*VBAT.

A logic bit transition must be less than 10% of the total bit time.

The transition time is measured between the 80% and 20%

battery points. Bit time is defined as the time between the 50%

battery points of consecutive rising and falling levels.

Car

Battery

www.vishay.com

2

Regulator

5V

VIN VOUT

GND

VDD

RXL

Micro

RXK

Processor

TX

VDD

Logic Circuitry

GND

VBAT

L-Line

K-Line

Diagnostic Tester

VBAT

510 W

VBAT/2

K

Si9243

BUS

FIGURE 4. Si9243EY Applications Circuit

Document Number: 70573

16-Jan-01

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