High Performance Automotive Sonar Intrusion – Data Sheet

AS8412

March 2001

Page 5 of 14

Low Level Output Voltage

Vol

-

-

-

0.5

0.5

0.5

V

V

V

Pins 1, 20

Pins 18, 19

Pins 17

Iol=3 mA

Iol=4 mA

Iol=12mA

High Level Output Voltage

Voh

4.0

-

-

V

Pins 1, 20

Ioh=-3 mA

High-Z Output Current

Ioz

-

-

10

µA

Pins

17,

18,

19

Vo=5V

Total Supply Current

Idd

-

-

0.65

1.0

1.0

1.6

mA

mA

SEL40K= 1

SEL40K= 0

crystal or clock

ceramic resonator

C1=C2=100pF

A.C. Electrical Characteristics

Parameter

Symbol

Min

Typ

Max

Units

Conditions

Power-on-reset width

50

500

500

-

-

-

70

530

800

ms

SEL40K= 0, resonator / clock

SEL40K= 1, clock

SEL40K= 1, crystal

1.3

1.7

1.7

-

-

-

1.4

1.9

2.1

s

SEL40K= 0, resonator / clock

SEL40K= 1, clock

SEL40K= 1, crystal

Fault indication pulse width

4.3

-

4.6

s

ALARM low pulse width

200

-

-

ms

Pins 18, 19

LED low pulse width

-

-

89

977

-

-

ms

ms

narrow = no detection

wide = detection

LED high pulse width

-

888

-

ms

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 AS8412 uses the sonar principle to

build a high-performance intrusion detector that follows the requirements of the OEM automo-

tive industry. As very short ultrasonic bursts are sent, the power needed to drive the transmitter

is reduced. Interference and signal cancellation effects, present in systems with continuous

transmission, are virtually eliminated.

Fig. 1 shows the pulse/echo timing generated by the AS8412.

The basic concept behind the AS8412 is the detection of changes in the relative position of

objects inside 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.