MAX1471 Maxim Integrated Products, MAX1471 Datasheet - Page 13

• Manufacturer Part Number: MAX1471
• Description: 3V/5V ASK/FSK Superheterodyne Receiver
• Manufacturer: Maxim Integrated Products

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Table 1. Component Values for Typical Application Circuit
Note: Component values vary depending on PC board layout.
Choosing standard capacitor values changes C
470pF and C
Circuit, C
ly, for ASK data, and C21 and C22 for FSK data.
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
COMPONENT
C
C
C10
C11
C12
C14
C15
C21
C22
C23
C26
C27
F1
C3
C4
C5
C6
C7
C8
C9
R3
R8
Y1
Y2
L1
L2
L3
F1
F2
and C
=
=
F2
(
( )(
1 414 100
4 100
.
to 220pF. In the Typical Application
F2
______________________________________________________________________________________
)(
are named C4 and C3, respective-
k
Ω
1 414
.
)(
VALUE FOR 433.92MHz RF
1 000
k
3 14 5
.
Ω
.
10.7MHz ceramic filter
ASK/FSK Superheterodyne Receiver
)(
3 14 5
)(
315MHz/434MHz Low-Power, 3V/5V
.
13.2256MHz
kHz
0.047µF
0.047µF
1500pF
0.01µF
)(
220pF
470pF
100pF
100pF
220pF
100pF
220pF
470pF
1.0pF
0.1µF
0.1µF
56nH
16nH
10nH
25kΩ
25kΩ
15pF
15pF
kHz
)
≈
Data Slicers
225
)
≈
pF
450
pF
F1
to
VALUE FOR 315MHz RF
10.7MHz ceramic filter
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
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.
9.509MHz
0.047µF
0.047µF
1500pF
0.01µF
100nH
220pF
470pF
100pF
100pF
220pF
100pF
220pF
470pF
0.1µF
2.2pF
0.1µF
30nH
15nH
25kΩ
25kΩ
15pF
15pF
Murata SFECV10.7 series
DESCRIPTION (%)
Coilcraft 0603CS
Coilcraft 0603CS
±0.1pF
Crystal
10
10
10
10
10
10
10
10
10
5
5
5
5
5
5
5
5
5
5
Figure
13