Datasheet AS8413 Datasheet (Austria Mikro Systeme International)

AS8413
HIGH PERFORMANCE

AUTOMOTIVE SONAR INTRUSION

Data Sheet
March 2001

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Key Features

• True sonar/pulse-echo operation

• Master/slave synchronization

• Wide dynamic range

• Programmable sensitivity levels

• Self-adaptive to vehicle interiors

• Self-adaptive to temperature and environmental changes

• High sensitivity to intrusion

• Immunity to false alarms

• Detection of sabotage attempts

• Compatible with standard 40 kHz ultrasonic transducers

• Specific for systems with multiple transducers

• No adjustments needed at factory or at field

• Few external components

• Time reference: external clock or oscillator based on crystal/ceramic resonator

• Built-in self-test

• Internal power-on-reset

• Advanced CMOS technology

• Low power consumption: 0.65 to 1.0 mA

• Operation between -40°C and +85 °C

• Available in 24-pin DIP and 24-pin SOIC package

General Description

The AS8413 is a signal processing IC designed to implement reliable, high-performance

sonar intrusion detectors. It generates short 40 kHz bursts to feed an ultrasonic trans­ducer. The resulting sonar waves are reflected on the vehicle interior and the echoes are
received by another transducer. Inside the AS8413, the electrical signal is first submitted to
an analog conditioning circuit, then it is digitized and processed by a DSP, whose output is
analyzed by a discriminator based on fuzzy-logic techniques. Thus, true intrusion condi­tions can be discerned from natural phenomena and other allowable disturbances.

Synchronization between the sonar waves from 2 or more pairs of transducers is made

possible by means of a master/slave configuration. Each pair is controlled by a AS8413 IC.

No adjustments are necessary at factory or at the field, as the AS8413 is self-adaptive to

the physical and environmental conditions. Compact and EMI-resistant intrusion detectors
are made possible, due to the small number of components.

Block Diagram

RX

PRE­AMP

BAND-PASS
FILTER

AGC

ENVELOPE
DETECTOR

A / D
CONVERTER

VCAP

TX1
TX2

SEL40K

OSCIN

OSCOUT

COSC
MODE
SYNC

MODULATOR /
DRIVER

OSCILLATOR SIGNALLING

CONTROL
LOGIC

D S P

DISCRIMINATOR

SAS
SENS 1
SENS 0

ALEN
LED
WARN
ALARM

March 2001 Page 2 of 15

High Performance Automotive Sonar Intrusion – Data Sheet

ALARM

abled).

tied to VDD for normal operation.

AS8413

Pin Description

AS8413
Pin # Name Description

1 TX1 40-kHz burst generator - output 1.
2 OSCIN Clock input or crystal / ceramic resonator connection.
3 OSCOUT Crystal / ceramic resonator connection. Not connected when external clock is ap-

plied.

4 COSC Clock output to slave IC
5 VCAP Pin for programming capacitor at the envelope detector.
6 AVDD Analog supply voltage (+5V).
7 AGND Analog ground.
8 RXGND Analog ground.
9 RX Ultrasonic echo input.
10 SEL40K Time reference select input (SEL40K=’1’ to select 40 kHz or SEL 40K=’0’ to select

400 kHz at OSCIN).

11 ALEN Alarm enable input (when ALEN =’0’, the outputs ALARM, WARN and LED are dis-

12 MODE Master/slave configuration pin (MODE=’0’ to configure slave IC, MODE=’1’ To confi g-

ure master IC with delayed sync and MODE open, to configure master IC without
delayed sync)

13 SENS0 Sensitivity selection (least significant bit).
14 SENS1 Sensitivity selection (most significant bit).
15 SAS SAS enable input (SAS=’1’ activates Self-Adjusting Sensitivity, SAS=’0’ keeps sens i-

tivity fixed)

16 N.C. (not connected)
17

TP

Test / reset pin. A rising edge resets the IC. This pin should be left unconnected or

18 VDD Digital supply voltage (+5V).
19 GND Digital ground
20 SYNC Synchronization pin. This pin is configured as output if pin MODE=’1^’ and as input if

MODE=’0’.

21
22

LED
WARN

Active-low signalling LED output (open drain).

Active-low auxiliary alarm output (open drain).
23 ALARM Active-low main alarm output (open drain).
24 TX2 40-kHz burst generator - output 2.

TX2

WARN

Pinout & Packaging

Change pinout according to
Pin Description.

Available Package(s):

• 24 pin SOIC

• (24 pin Skinny DIP)

LED
SYNC
GND
VDD
TP
N.C.
SAS
SENS1
SENS0

March 2001 Page 3 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Absolute Maximum Ratings

Conditions: 1. AII voltages referenced to GND

2. AVDD connected to VDD

3. AGND connected to GND

Supply Voltage < 7V
Input Pin Voltage -0,3 V to VDD + 0.3 V
Output Pin Voltage -0,3 V to VDD + 0.3 V
Power dissipation 500 mW
Operating temperature under bias -40 °C to +85 °C
Storage Temperature -65 °C to +150 °C
Latch-up immunity -10mA … + 10mA

Note: Stresses above these values may cause permanent damage to the device.
Functional operational at these values is not implied
ESD immunity / HBM; 1500 Ohm; 100 pF

Recommended Operating Conditions

Parameter Symbol Min Typ Max Units
Supply Voltage (VDD, AVDD) V
Operating Temperature Range T
Clock Frequency (SEL40K=1) F
AC Peak Voltage at RX Input V

DD

O

CK

IN

4.5 5.0 5.5 V

-40 - 85 °C
39 40 41 kHz

0.1 - 10 mV

D.C. Electrical Characteristics
(V

= 5 V, V

DD

= Ground, TA = -40 °C to +85 °C)

SS

Parameter Symbol Min Typ Max Units Conditions
Low Level Input Voltage V
High Level Input Voltage V
Low Level Input Voltage V
High Level Input Voltage V

il

ih

il

ih

- - 1.5 V Pins 2, 10, 13, 14, 15, 20

3.5 - - V Pins 2, 10, 13, 14, 15, 20

- - 0.5 V Pin 12

4.5 - - V Pin 12
Low-to-High Threshold V
High-to-Low Threshold V
Hysteresis V
Low Level Input Current I

High Level Input Current I
Input Resistance R

t+

t-

h

il

ih

in

- 3.0 3.5 V Pin 11 (Schmitt Trigger Input)

1.4 1.8 - V Pin 11 (Schmitt Trigger Input)

0.6 - - V Pin 11

-1 - - µA Pins 10, 11, 13, 14, 15 (V

- - 1 µA Pins 10,11, 13, 14, 15 (V

DD

DD

=5 V)

=5V)

- 200 - kΩ Pin 9

March 2001 Page 4 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Low Level Output Voltage Vol -

-

-

0.5

0.5

0.5

V
V
V

Pins 1, 20, 24
Pins 22,23
Pins 21

Iol=3 mA
Iol=4 mA

Iol=12mA
High Level Output Voltage Voh 4.0 - - V Pins 1, 20, 24 Ioh=-3 mA
Low Level Output Voltage V

High Level Output Voltage V

High-Z Output Current I
Total Supply Current I

ol

oh

oz

dd

-

-

4.6

3.5

-

0.4

-

1.5

-

-

-

-

V V Pin 4 (SEL40K= 0)

Pin 4 (SEL40K= 1)

V V Pin 4 (SEL40K= 0)

Pin 4 (SEL40K= 1)

- - 10 µA Pins 21, 22, 23 V

-

0.65

-

1.0

1.0

1.6

mA
mA

SEL40K= 1
SEL40K= 0

I

=100uA

ol

I

=10 uA

ol

I

=-100 uA

oh

I

=-10 uA

oh

=5V

o

crystal or clock

ceramic resonator

C1=C2=100pF

A.C. Electrical Characteristics
(V

= 5 V, V

DD

= Ground, TA = 25°C)

SS

Parameter Symbol Min Typ Max Units Conditions
Power-on-reset width t

Self-test delay (incl. t

) t

por

Fault indication pulse width t
SYNC pulse width t
SYNC period T

por

std

stw

sync

sync

50
500
500

1.3

1.7

1.7

-

-

-

-

-

-

70
530
800

1.4

1.9

2.1

ms

s SEL40K= 0, resonator / clock

4.3 - 4.6 s

- 0.6 - ms

- 44.4 - ms

SEL40K= 0, resonator / clock
SEL40K= 1, clock
SEL40K= 1, crystal

SEL40K= 1, clock
SEL40K= 1, crystal

ALARM low pulse width t
LED low pulse width t

LED low pulse width t

onn

t

onw

200 - - ms Pins 22, 23

al

-

-

off

- 888 - ms

89

977

-

-

ms

narrow = no detection

ms

wide = detection

System Description

Ultrasonic intrusion detectors are very popular in vehicle security systems, due to their low cost,

good area coverage and easiness of installation. The AS8413 uses the sonar principle to build a
high-performance intrusion detector that follows the requirements of the OEM automotive indus­try. Additionally, the IC supports the use of two or more pairs of sensors. As very short ultrasonic
bursts are sent, the power needed to drive the transmitter is reduced. Interference and signal
ancellation effects, present in systems with continuous transmission, are virtually eliminated.

March 2001 Page 5 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Fig. 1 shows the pulse/echo timing generated by the AS8413. The basic concept behind the

AS8413 is the detection of changes in the relative position of objects in side the vehicle, by
monitoring successive echo patterns with a discriminator based on fuzzy-logic.

Despite the higher complexity of this approach, that demands both analog and digital signal

processing, the solution is made cost-effective with the use of a single IC and a small number of
external components

0,6ms

TX pulse

44,4ms

Echo in RX

Fig. 1 - Pulse/Echo Timing

Supply / Power-On Reset

The AS8413 requires a single 5-volt power supply. Pins for VDD and GND are separated for the

analog and digital circuits, and a 100-n-F ceramic decoupling capacitor is recommended for
each pair.

There is an internal power-on-reset circuit that initializes the IC after each power-up. The VDD

rise time must be less than 20 ms, to guarantee proper initialization. Optionally, the IC can also
be reinitialized with a rising-edge at the pin 17, if requested by the application.

Time Reference

A clock must be present at the OSCIN input. The frequency may be selected to be either 40 kHz

or 400 kHz, by setting the SEL40K input to ‘1’ or ‘0’ respectively. For the 40 kHz clock a duty­cycle of approximately 50% is necessary.

The clock signal can be created in several possible ways:

• Generation by a microprocessor or other external circuit

• Built-in oscillator with an external 40-kHz crystal between OSCIN and OSCOUT. Depending

on the crystal, a load capacitor (about 22 pF) may be needed at OSCOUT.

• Built-in oscillator with an external 400-kHz ceramic resonator between OSCIN and OSCOUT.
Load capacitors of at least 100 pF are necessary at the pins, according to the resonator
specifications. The IC power consumption increases with higher capacitor values (Idd= 1.0
mA with 100 pF capacitors).

March 2001 Page 6 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Optionally one of the AS8413 ICs used in a system may have its built-in oscillator and generate

clock to the other IC from its COSC output. A driver would be needed, if IC’s are not adjacent.

Master/slave synchronization

The AS8413 is intended to be used in intrusion detector systems where more than one pair of

transducers is used. Each IC is able to control a single transmitter /receiver pair. In multiple­transducer systems it is necessary that the bursts generated by each transmitter are synchro­nized. Otherwise, the echoes may slip over each other and cause undesirable effects, such as
false alarms.

Each AS8413 IC can be programmed to be either a master that generates an external delayed

sync signal or a slave. This signal may come from the master or from an external circuit, such
as a microcontroller. The sync signal received at the slave is delayed by half transmission period
(22.2 ms) to the internal sync signal used by the master, in order to avoid burst superposition as
much as possible.

The AS8413 can be configured to operate under 3 possible conditions, by programming the

MODE input in one of the three possible conditions:

• logic ‘0’: slave (receives delayed sync)

• logic ‘1’: master in a multi-pair system (generates delayed sync)

• open: master in a single-pair system (AS8412 mode)

Ultrasonic Transducers

The AS8413 is compatible with standard 40-kHz ultrasonic transducers, available from several

manufacturers. For each IC, one transducer is used to transmit the sonar pulses and one other
to receive the echoes reflected inside the vehicle. Internal lengths up to 3.5 meters can be co v­ered.

In most applications, just two pairs of sensors will be used. The sensors will typically be posi-

tioned at the B-pillars (central pillars), close to the roof, to provide the best possible coverage of
all the vehicle interior. Each pillar may have either a transmitter/receiver pair or two sensors of
the same kind. The first arrangement is recommended, as it allows a single box at each pillar
containing the AS8413 and the transducer pair controlled by it, thus decreasing cabling.

The outputs TX1 and TX2 drive the transmitter in a push-pull configuration with 10 V peak-to-

peak. As shown in Fig. 1, the transmission duty-cycle is very short (around 1/75), reducing the
average current needed to generate the ultrasonic bursts to about 0.05 mA per IC.

Shielded cable is mandatory for the receiver and recommended for the transmitter, unless they

are adjacent to the IC. The shield at the receiver cable must be grounded and connected to the
RXGND pin.

March 2001 Page 7 of 15

High Performance Automotive Sonar Intrusion – Data Sheet

VDD

AS8413

Analog Conditioning

The analog front-end, composed of a preamplifier and a filter centered at 40 kHz, increases the

signal level and removes noise outside the bandpass. It is followed by a digitally-controlled AGC
amplifier, that keeps signal level at the VCAP output within prescribed levels. Finally, an envelope
detector extracts the information embedded in the amplified echo signal.

The front-end needs proper bias during power-up. That can be provided by an RC series circuit

to VDD, as shown at Fig. 2, or alternatively, by the pre-amplifier of Fig. 4.

100n

100k

To RX-Pin

Fig. 2 - Series-RC circuit at RX

The AS8413 has a wide dynamic range, to follow the signal fluctuations that occur in a large

variety of vehicles, sensors and environmental conditions. Only under extreme conditions, like in
a larger vehicle, an external pre-amplifier at RX may help to improve performance.

A practical way to verify if a pre-amplifier might be useful, is by monitoring the echo waveform at

VCAP. For measuring that voltage a FET-input buffer (input impedance at least 109 ohm) should
be used, as the output impedance at VCAP is very high.

A pre-amplifier that satisfies the bias requirements is shown at the Fig. 4. Its gain is around 8 dB.

VCAP(V)

3,0V-4,2V

1,3V-1,8V

0

10 20

Period = 44,4 ms

30 40 T(ms)

Fig. 3 - Waveform at VCAP

March 2001 Page 8 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Fig. 4 - Recommended pre-amplifier

As a general rule, the best approach is to measure the voltage at the “valley”, that normally oc-

curs at the end of the echo waveform. If it is above 1.8 V, then the system could benefit from
some extra gain.

Sensitivity Programming

The AS8413 allows the sensitivity to intrusions and movements to be programmed at produc-

tion, so the manufacturer can adapt the detector to different requirements.

There are two possible ways of programming the sensitivity:

• Digital programming by the pins SENS1 and SENS0: controls the criteria used by the dis­criminator to validate intrusions or movements. Four sensitivities are available, as shown at
Table 1.

Table 1. Digital programmable sensitivities

SENS1

1
1
0
0

SENS0

1
0
1
0

Sensitivity
High
Mid-high
Mid-low
Low

• Capacitor at the pin VCAP: controls the analog processing of the echo signal at the envelope
detector. With smaller capacitors, the digitized echo signal will have a higher resolution and,
as a result, a higher sensitivity will be obtained.

The best combination of digital programming and VCAP capacitor is usually determined by

experiment. A generally good choice is to use sensitivity mid-high with a 270-pF capacitor at
VCAP.

March 2001 Page 9 of 15

High Performance Automotive Sonar Intrusion – Data Sheet

SENSITIVITY

AS8413

Table 2 shows some possible sensitivity combinations, marked according to the expected

behavior at the field. It should be used as a guide to determine the best combination for each
application.

Table 2. Sensitivity as Function of Digital and VCAP Programming

PROGRAM 390 pF 330 pF 270 pF 220 pF
High OK OK + +
Mid-high - OK OK +
Mid-low - - OK OK
Low - - - OK

(+) positions with higher sensitivities; may present false alarms under extreme conditions
(OK) most usual sensitivity combinations
(-) positions with lower sensitivities; may be useful for specific applications

The Self-Adjusting Sensitivity (SAS)

The SAS (Self-Adjusting Sensitivity) control loop is a powerful feature that optimizes the sensitiv-

ity to intrusion and motion, based on the present environmental conditions. Under quiet situations
the detector has a very high sensitivity. On the other hand, when certain disturbances such as
thermal gradients appear inside the vehicle, the sensitivity is drecreased to avoid possible false
alarms.

The sensitivity range programmed by the manufacturer is not changed by the SAS, that simply

selects the most adequate sensitivity for each situation within the allowed range. Fig. 5 gives a
rough idea of how the SAS can affect the detector sensitivity, for a given capacitor at VCAP.

HIGH

MID-HIGH

MID-LOW

LOW

Fig. 5 - Sensitivity Ranges with SAS

The SAS actuation is controlled by the SAS input.

• SAS enabled (pin SAS = “1”):

After power-on, the IC starts with the lowest sensitivity within the programmed range. The

sensitivity will be constantly adjusted, according to the external conditions. Even under quiet
conditions, the IC may take at least 2 minutes to reach the maximum allowed sensitivity. That
should be considered during system evaluation.

March 2001 Page 10 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

• SAS disabled (pin SAS = “0”)

The IC will keep the sensitivity fixed at the upper limit of the programmed range, regardless of

the environmental conditions. This mode can be useful in special applications that demand a
fixed or externally controlled sensitivity. The VCAP capacitor may have to be up to 4 times
bigger than it would be with the SAS enabled, to compensate the fixed high sensitivity and
avoid false alarms. Another use of this mode is to allow an easier characterization of the up­per sensitivity limit during the system development.

The self-test indicates an error with SAS = ”0”. To generate a valid self-test, SAS must be “1”

during power-up. It may be switched afterwards.

Together with the AGC, the SAS loop provides improved controllability over the intrusion detec-

tion process, allowing the system to be little affected by changes in the external conditions, such
as temperature, supply voltage and sensitivity of the ultrasonic sensors.

In any case, the sensitivity can be very significant, so the AS8413 is not adequate to be used in

convertibles or with open windows.

DSP and Fuzzy-Logic Discriminator

Many external phenomena may affect the ultrasonic waves inside the vehicle. Sunlight, blows at

the glasses or roof, wind through the ventilation flaps are some examples.

Experiments have shown that a real intrusion can not be validated by a single specific charac-

teristic of the echo waveform. Several parameters must be observed at the same time and also
how they correlate with each other. Experimental data gathered from extensive field testing were
used to support the detection criteria embedded in the AS8413.

To implement those criteria, first the digitized echoes are processed by a DSP circuit to en-

hance the parameters to be monitored. Then, a fuzzy-logic discriminator continuously examines
how those parameters change and correlate, to verify any possible intrusion.

Built-In-Self-Test

When power is applied and SAS=’1’, the master AS8413 goes automatically into a self-test rou-

tine that checks the IC operation. It can also detect initialization errors due to a slow supply rise
time or a clock problem at OSCIN. The self-test does not operate in a slave IC.

During the self-test period, the IC outputs are exercised and should be ignored. If the test is su c-

cessful, normal operation starts, indicated by the output LED pulsing periodically.

In the case of an IC malfunction, immediately after the self-test the LED and WARN outputs are

turned on (low) for about 4.4 seconds. If a light-emitting diode is connected to the LED output,
the self-test message may be seen directly by the user.

After an error message, the LED starts to blink again, as in a normal operation. Fig. 6 shows the

possible self-test waveforms after power-on.

March 2001 Page 11 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

VDD

WARN

DON’T CARE

DON’T CARE

t

s t d

t

of f

t

o n n

( a )

VDD

WARN

DON’T CARE

DON’T CARE

t

s t d

t

s t w

t

o f f

t

o n n

( b )

Fig. 6
(a) Self-Test OK
(b) Error at Self-Test

Alarm Signalling

The AS8413 can indicate not only intrusion or motion, but also other kinds of disturbance, and

send a particular message for each situation. Those disturbances are defined as follows and the
messages are identified at Table 3.

• Weak intrusion: early stages of an intrusion, or a weaker intrusion or movement. Detection
criteria are similar to those for intrusion, but with higher sensitivity.

• Blockage: elimination of the coupling between the transducers, either by blocking one of
them, or by cutting a wire.

• Saturation: very strong 40-kHz signal at RX, possibly an attempt to sabotage the alarm sy s­tem by saturating the receiver. May also be caused by a glass breakage or by strong hits with
hard objects at the glass.

With this signalling scheme, the IC has flexibility to be used either in simpler applications or in
sophisticated microprocessor based systems. In addition, the manufacturer has the option to
choose which kind of disturbance should be an alarm condition.

The pulse widths are those specified in the AC electrical Characteristics and shown in Fig. 7. At
ALARM and WARN they are at least 200ms; the outputs remain active if intrusion or motion per­sists.

The WARN output could be used instead of the ALARM, if only intrusion detections should be
flagged. In this case, the digital sensitivity should be scaled one step ower (for instance from
mid-high to mid-low), or the capacitor at VCAP increased, to keep approximately the same se n­sitivity.

March 2001 Page 12 of 15

High Performance Automotive Sonar Intrusion – Data Sheet

talt

AS8413

The blockage and saturation are signalized just one time at each occurrence, to avoid continu­ous alarm triggering. Detection of glass breakage by saturation is not guaranteed.

Table 3. Disturbances detected by the AS8413

LED ALARM WARN Conditions
pulsing 1 1 no disturbance
pulsing 1 0 weak intrusion
0 0 0 intrusion
pulsing 0 1 blockage
0 0 1 saturation

al

WARN

t

al

ALARM

t

ONW

t

ONN

Fig. 7 - Weak Intrusion Followed by an Intrusion

Courtesy Entry/Exit Time

The pin ALEN is an optional alarm enable input that can be used to provide a courtesy entry
and/or exit time. When tied to VDD, normal alarm operation is enabled. If ALEN is grounded, the
outputs ALARM, WARN and LED are disabled, except during the self-test, when LED indicates
the test result.

By grounding ALEN, the IC can be made inoperative as seen by the control unit and still keep its
internal processing. This is useful when intrusion detections must be temporarily inhibited, or to
block self-test pulses at ALARM and WARN.

During the first 10 or 20 seconds after shutting a door in a hot and sunny day, an alarm indica­tion may occur, due to thermal gradients inside the vehicle. That sould be considered when
choosing a courtesy time for a AS8413-based system. When a RC circuit connected to the
supply voltage is applied to ALEN, the courtesy time after power-up is given by:

T≈0.92 x R x C

March 2001 Page 13 of 15

High Performance Automotive Sonar Intrusion – Data Sheet
AS8413

Application Circuit

A typical Application Circuit for the AS8413 is presented at Fig. 8, where a 400 kHz oscillator with
external ceramic resonator is built for each IC. This circuit is suitable to be used in a microco n­troller-based alarm system.
Optionally, the microcontroller could synthesize a 40 kHz for the ICs, decreasing component
count and power at the system level. The digital sensitivity also can be controlled, in specific
applications.
If access to all the signalling outputs of both ICs is provided, the alarm system will be able to
identify the kind of disturbance detected and the region where it occurred.

Res.

400kHz

Res.

400kHz

270p

RX

270p

RX

TX

M

100 p

100p

M

TX

S

100 p

100p

S

100n

VDD

100n

VDD

VDD

VDD

1
2
3
4
5
6
7
8
9

10

11

12

1
2
3
4
5
6
7
8
9

10

11

12

TX1
OSCIN
OSCOUT
COSC
VCAP
AVDD
AGND
RXGND
RX
SEL4OK
ALEN
MODE

(MASTER)

TX1
OSCIN
OSCOUT
COSC
VCAP
AVDD
AGND
RXGND
RX
SEL4OK
ALEN
MODE

TX2

ALARM

WARN

LED

SYNC

GND

VDD

TP
N.C.
SAS

SENS1
SENS0

TX2

ALARM

WARN

LED

SYNC

GND

VDD

TP
N.C.
SAS

SENS1
SENS0

VDD

24

56k

23
22

330

21
20
19

100n

18
17
16

VDD

15
14
13

VDD
24
23
22

330

21
20
19

100n

18
17
16

VDD

15
14
13

VDD

VDD

56k

VDD

VDD

(SLAVE)

Fig. 8 - Application Circuit

March 2001 Page 14 of 15

High Performance Automotive Sonar Intrusion – Data Sheet

VDD

AS8413

EMI Protection

The usual precautions against EMI, such as PCB with ground plane, short tracks and shielded
cables, are recommended for AS8413 applications, to avoid possible effects from noise induced
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 connected
to TX1 and the shield connected to TX2. In this case, only the TX2 output will need protection
diodes

IC

(a) (b)

Fig. 9 - Diode Clamp Protection for
Unshielded Cables
(a) pins 1, 24
(b) pins 21, 22, 23

IC

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.

March 2001 Page 15 of 15