ams AG AS3932 Installation and operating instructions

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3D Low Frequency Wakeup Receiver
AS3932 APPLICATION NOTE
Application Note AS3932
Migration from ATA5283 (1-channel) to AS3932
Date: 09/02/2009
Revision: 1.0
Copyright © 2009 austriamicrosystems
ams AG
Technical content still valid

Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
Contents
1INTRODUCTION..........................................................................................................................3
2COMPARISON OF THE HARDWARE .....................................................................................3
2.1 APPLICATION DIAGRAMS...........................................................................................................3
2.2 OSCILLATOR FREQUENCY..........................................................................................................4
2.3 SERIAL DIGITAL INTERFACE......................................................................................................5
2.4 WAKEUP AND DATA PIN ............................................................................................................5
2.5 MANCHESTER CLOCK RECOVERY ..............................................................................................5
3PROTOCOL COMPATIBILITY.................................................................................................5
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Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
1Introduction
This document shows how to easily migrate from ATA5283 to AS3932.
2Comparison of the Hardware
2.1 Application diagrams
The figures 2-1 and 2-2 show the application diagram of ATA5283 and AS3932, respectively.
Figure 2-1: Application diagram of ATA5283
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Figure 2-2: Application diagram of AS3932
ATA5283 is a single channel wakeup receiver, while AS3932 has three channels available. Therefore it is
mandatory to connect the channels 2 and 3 (LF2P and LF3P) of AS3932 to a fixed DC potential (either GND or
VCC) and to disable them in the register map via SDI (see chapter 3). The ATA5283 application block diagram
shows that the input antenna has to be referenced to the positive supply, while the AS3932 block diagram shows
that the inputs are referenced to ground. In addition AS3932 offers the possibility to reference the input to the
positive potential,, as shown in the next figure 2-3. This modification will not influence the performance of AS3932.
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Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
Figure 2-3: Alternative application diagram of AS3932.
2.2 Oscillator frequency
The ATA5283 has no Real Time Clock (RTC), while the AS3932 has a RTC that either uses a crystal oscillator or
the fully integrated RC oscillator. In case a crystal oscillator is used, a 32768 Hz quartz and two capacitors
(specified by the crystal manufacturer) are needed for AS3932.
AS3932 also offers the possibility to define the oscillator frequency using the internal RC-oscillator. This oscillator
can be calibrated with the microcontroller (see p. 27 of AS3932 data sheet) in order to increase its precision. In
this case the XIN and XOUT have to be connected to the positive supply voltage, as shown in figure 2-4.
VCC
LF1P
LF2P
LF3P
LFN
VSS GND
XIN
XOUT
WAKE
DAT
CL_DAT
CS
SCL
SDI
SDO
CBAT
X, Y AND Z RECEIVING ANTENNAS
TX
TRANSMITTER
TRANSMITTING ANTENNA
AS3932
VCC
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Figure 2-4: Application diagram of AS3932 in case the RC-oscillator is used.
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Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
2.3 Serial Digital Interface
The AS3932 has a 4-wire serial data interface (CS, SDI, SDO, SCL) while the ATA5283 has no interface,
since no programmability is allowed. The Serial Digital Interface of AS3932 needs to be programmed accordingly
(see p. 16 to p. 18 of AS3932 data sheet).
2.4 Wakeup and data pin
Both AS3932 and ATA5283 have two dedicated pins for the wakeup and data; the only difference is that the
wakeup pin of ATA5283 (WAKEUP) has an inverted meaning compared to AS3932 (WAKEUP=high=no wakeup,
WAKEUP=low=wakeup)
2.5 Manchester clock recovery
Furthermore the AS3932 has a fully integrated Manchester clock recovery, which provides the recovered clock
on the pin CL_DAT. This pin is missing in the ATA5283, thus no clock recovery is possible. In case clock recovery
is not required, the pin CL_DAT of AS3932 can remain floating.
3Protocol compatibility
The ATA5283 wakes up if a carrier burst of at least 704 periods is followed by a “start gap” (no Signal); an
example is given in the figure 3-1.
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Figure 3-1: ATA5283 wakeup protocol description
In order to have full compatibility to ATA5283, AS3932 should be set to frequency detection only (R1<1>=0). In
this way the AS3932 will react to the presence of the carrier signal (WAKE signal goes high as soon as the carrier
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Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
signal is detected). The minimum duration of the carrier burst is 360us for AS3932. To wake the AS3932 up, no
“start gap” is needed, as shown in the figure 3-2.
Figure 3-2: AS3932 wakeup protocol description
The procedure to set up the AS3932 working in this way is described below.
•Send the preset_default direct command
•Write in the register R0<7:0> 02 (HEX) This ensures that Channel 2 and Channel 3 are disabled in order to
reduce the current consumption.
•Write R1<7:0> 21 (HEX) in case the crystal oscillator is used or write R1<7:0> 20 (HEX) if the RC oscillator is
used. In this way the wakeup will occur only based on frequency detection.
•Set the envelop detector time constant (R3<2:0>) according to the used bit rate (see p. 20 of AS3932 data
sheet).
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Application Note AS3932 - Migration from ATA5283 (1-channel) to AS3932
Contact
austriamicrosystems AG
A 8141 Schloss Premstaetten, Austria
T. [phone]
F. [phone]
[email protected]om
Copyright © 2009 austriamicrosystems
Copyright
Copyright © 2009 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. austriamicrosystems reserves the right to discontinue production and change specifications
and prices, make corrections, modifications, enhancements, improvements and other changes of its products and
services at any time without notice.
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