High Performance Automotive Sonar Intrusion – Data Sheet

AS8412

March 2001

Page 14 of 14

The Application Circuit II of Fig. 8b can be used in a simpler system, that does not need micro-

controller. A 400-kHz oscillator is built with a ceramic resonator. By using just the ALARM out-

put, the system is able to detect intrusion, blockage and saturation as alarm of the operation

and of the IC self-test diagnostic. A courtesy time is provided by R3 and C7.

EMI Protection

The usual precautions against EMI, such as PCB with ground plane, short tracks and shielded

cables, are recommended for AS8412 applications, to avoid possible effects from noise in-

duced by external sources.

The RX cable must be shielded, because of the low-voltage signal. An alternative to protect

other pins directly connected to unshielded cables, is to clamp induced voltages with signal

diodes close to the pins (Fig.9)

If a single shielded cable is used for the transmitting sensor, the internal wire may be con-

nected to TX1 and the shield connected to TX2. In this case, only the TX2 output will need pro-

tection diodes

IC

VDD

(a)

(b)

Fig. 9 - Diode Clamp Protection for

Unshielded Cables

(a) pins 1, 20

(b) pins 17, 18, 19

Copyright

© 2000, Austria Mikro Systeme International AG, Schloß Premstätten, 8141 Unterpremstätten, Austria.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by

any means, without the prior permission in writing by the copyright holder. To the best of its knowledge, Austria Mikro Systeme

International asserts that the information contained in this publication is accurate and correct.

IC