AS3930-BQFT austriamicrosystems, AS3930-BQFT Datasheet - Page 20

• Manufacturer Part Number: AS3930-BQFT
• Description: IC RF PROGRAM RECEIVER 16-QFN
• Manufacturer: austriamicrosystems

Specifications of AS3930-BQFT

• Rf Type: Read / Write
• Frequency: 110kHz ~ 150kHz
• Features: RSSI Equipped
• Package / Case: 16-VFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AS3930-BQFTTR

AS3930
Data Sheet - D e t a i l e d D e s c r i p t i o n
If the bit rate gets higher, the time constant in the envelop detector must be set to a smaller value, this means that higher noise is injected
because of the wider band. The next table is a rough indication of how the envelop detector looks like for different bit rates. By using proper data
slicer settings it is possible to improve the noise immunity paying the penalty of a longer preamble. In fact if the data slicer has a bigger time
constant it is possible to reject more noise, but every time a transmission occurs, the data slicer need time to settle. This settling time will
influence the length of the preamble.
Table 17. Bit setup for Data Slicer for Different Preamble Length
Note: These times are minimum required, but it is recommended to prolong the preamble.
The comparator of the data slicer can work only with positive or with symmetrical threshold (R3<6>). In addition the threshold can be 20 or 40 mV
(R3<7>)
In case the length of the preamble is an issue the data slicer can also work with an absolute threshold (R1<7>). In this case the bits R3<2:0>
would not influence the performance. It is even possible to reduce the absolute threshold in case the environment is not particularly noisy
(R2<7>).
8.6 Correlator
After frequency detection the data correlation is only performed if the correlator is enabled (R1<1>=1).
The data correlation consists of checking the presence of a preamble (ON/OFF modulated carrier) followed by a certain pattern.
After the frequency detection the correlator waits 16 bits (see bit rate definition in
listening mode and the false-wakeup register (R13<7:0>) is incremented by one.
To get started with the pattern correlation the correlator needs to detect at least 4 bits of the preamble (ON/OFF modulated carrier).
The bit duration is defined in the register R7<4:0> according to the
Table 18. Bit Rate Setup
www.austriamicrosystems.com/AS3930
R7<4>
0
0
0
0
0
0
0
0
0
0
0
R3<5>
0
0
0
0
1
1
1
1
R7<3>
0
0
0
0
0
1
1
1
1
1
1
R7<2>
0
1
1
1
1
0
0
0
0
1
1
R3<4>
0
0
1
1
0
0
1
1
R7<1>
Table 17
1
0
0
1
1
0
0
1
1
0
0
gives a correlation between data slicer setup and minimum required preamble length.
R7<0>
1
0
1
0
1
0
1
0
1
0
1
R3<3>
Bit duration in RTC
0
1
0
1
0
1
0
1
clock periods
Table 18
10
11
12
13
14
Revision 1.0
4
5
6
7
8
9
as function of the Real Time Clock (RTC) periods.
Table
18) and if no preamble is detected the chip is set back to
Bit rate (bits/s)
Minimum preamble length [ms]
8192
6552
5460
4680
4096
3640
3276
2978
2730
2520
2340
1.15
1.55
2.65
0.8
1.9
2.3
3.5
3
Symbol rate (Manchester
symbols/s)
4096
3276
2730
2340
2048
1820
1638
1489
1365
1260
1170
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