MAX1471_05 Datasheet, PDF (13/26 Pages) Maxim Integrated Products – 315MHz/434MHz Low-Power, 3V/5V ASK/FSK Superheterodyne Receiver

315MHz/434MHz Low-Power, 3V/5V
ASK/FSK Superheterodyne Receiver
Table 1. Component Values for Typical Application Circuit
COMPONENT
C3
C4
C5
C6
C7
C8
C9
C10
C11
C12
C14
C15
C21
C22
C23
C26
C27
L1
L2
L3
R3
R8
Y1
Y2
VALUE FOR 433.92MHz RF
220pF
470pF
0.047µF
0.1µF
100pF
100pF
1.0pF
220pF
100pF
1500pF
15pF
15pF
220pF
470pF
0.01µF
0.1µF
0.047µF
56nH
16nH
10nH
25kΩ
25kΩ
13.2256MHz
10.7MHz ceramic filter
Note: Component values vary depending on PC board layout.
VALUE FOR 315MHz RF
220pF
470pF
0.047µF
0.1µF
100pF
100pF
2.2pF
220pF
100pF
1500pF
15pF
15pF
220pF
470pF
0.01µF
0.1µF
0.047µF
100nH
30nH
15nH
25kΩ
25kΩ
9.509MHz
10.7MHz ceramic filter
DESCRIPTION (%)
10
5
10
10
5
5
±0.1pF
10
5
10
5
5
10
5
10
10
10
Coilcraft 0603CS
Coilcraft 0603CS
5
5
5
Crystal
Murata SFECV10.7 series
C_F1
=
1.000
(^1.414)(^100kΩ)(^3.14)(^5kHz)
≈
450pF
C_F2
=
1.414
(⁴)(^100kΩ)(^3.14)(^5kHz)
≈
225pF
Choosing standard capacitor values changes C_F1 to
470pF and C_F2 to 220pF. In the Typical Application
Circuit, C_F1 and C_F2 are named C4 and C3, respective-
ly, for ASK data, and C21 and C22 for FSK data.
Data Slicers
The purpose of a data slicer is to take the analog output
of a data filter and convert it to a digital signal. This is
achieved by using a comparator and comparing the ana-
log input to a threshold voltage. The threshold voltage is
set by the voltage on the DSA- pin for the ASK receive
chain (DSF- for the FSK receive chain), which is connect-
ed to the negative input of the data slicer comparator.
Numerous configurations can be used to generate the
data-slicer threshold. For example, the circuit in Figure
4 shows a simple method using only one resistor and
one capacitor. This configuration averages the analog
output of the filter and sets the threshold to approxi-
mately 50% of that amplitude. With this configuration,
the threshold automatically adjusts as the analog signal
varies, minimizing the possibility for errors in the digital
data. The sizes of R and C affect how fast the threshold
tracks to the analog amplitude. Be sure to keep the cor-
ner frequency of the RC circuit much lower than the
lowest expected data rate.
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