AS8413 Просмотр технического описания (PDF) - austriamicrosystems AG

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AS8413

HIGH PERFORMANCE AUTOMOTIVE SONAR INTRUSION

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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

TX pulse

0,6ms

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 duty-

cycle 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

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