Revision No. 1.1, Date: 09-2005

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Copyright © 2005 austriamicrosystems. Trademarks registered ®. All rights reserved. The material herein may not be reproduced, adapted,

merged, translated, stored, or used without the prior written consent of the copyright owner. To the best of its knowledge,

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

1. General Description

AS3931 is an ultra low power, three channel LF ASK

receiver designed to operate in various applications

such as LF identification systems and LF tag receivers.

AS3931 is able to detect a low frequency ASK-

modulated signal by looking for a digital wake-up pattern

and generates a WAKE signal after successful pattern

detection. The device incorporates an intelligent pattern

detection algorithm that provides reliable operation even

in presence of strong interferences. RSSI signals can be

generated at the RSSI pin for each receiver channel.

2. Key Features

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3D wake-up pattern detection

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3D LF field strength measurement

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Antenna rotation for easy calibration

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High sensitivity and high dynamic range

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Wide operating frequency range

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Reliable, interference resistant wake-up decoding

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Highly protected differential inputs

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Ultra low power consumption

3. Main characteristics

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Wake-up sensitivity: 350 µVpp

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LF carrier frequency range: 19 – 150 kHz

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Data rate: 2.731 kb/s

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Current consumption in standby mode: 6.6 µA

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Dynamic range: 60 dB

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RSSI step: (

4. Additional Features

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Antenna rotation switch

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three independent LF receiver chains

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Wake-up output combining the three receiver

chains

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Low power 32.768 kHz crystal oscillator circuit

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Serial programming interface

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Voltage regulator with 2.4 V output, on/off

switchable

Each independent LF receiver chain contains:

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Input overload protection

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Input attenuator

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Ultra low power LF amplifier with logarithmic

envelope output

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Robust data detector with adaptive slicing

threshold that translates the logarithmic

envelope into a digital data signal

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Error tolerant digital pattern correlator that

detects a given code sequence in the received

data signal and generates a wake-up signal

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Sophisticated power management logic that

powers down the correlator if no data is

received

5. Applications

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LF identification systems

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LF tag receivers

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Three-dimensional LF field strength

measurement systems

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Ultra low power wake-up systems

3D Low Power Wake-up Receiver

AS3931

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