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參數(shù)資料
| 型號： | MAX7033 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Quadruple 2-Line To 1-Line Data Selectors/Multiplexers 16-CFP -55 to 125 |
| 中文描述： | 315MHz/433MHz ASK超外差接收器，帶有AGC鎖存 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 849K |
| 代理商： | MAX7033 |
designed to operate with higher differential load capac-
itance always pull the reference frequency higher. For
example, a 4.7547MHz crystal designed to operate
with a 10pF load capacitance oscillates at 4.7563MHz
with the MAX7033, causing the receiver to be tuned to
315.1MHz rather than 315.0MHz, an error of about
100kHz, or 320ppm.
In actuality, the oscillator pulls every crystal. The crys-
tal’s natural frequency is really below its specified fre-
quency, but when loaded with the specified load
capacitance, the crystal is pulled and oscillates at its
specified frequency. This pulling is already accounted
for in the specification of the load capacitance.
Additional pulling can be calculated if the electrical
parameters of the crystal are known. The frequency
pulling is given by:
where:
f
P
is the amount the crystal frequency pulled in ppm.
C
M
is the motional capacitance of the crystal.
C
CASE
is the case capacitance.
C
SPEC
is the specified load capacitance.
C
LOAD
is the actual load capacitance.
When the crystal is loaded as specified, i.e., C
LOAD
=
C
SPEC
, the frequency pulling equals zero.
It is possible to use an external reference oscillator in
place of a crystal to drive the VCO. AC-couple the exter-
nal oscillator to XTAL2 with a 1000pF capacitor. Drive
XTAL2 with a signal level of approximately -10dBm. AC-
couple XTAL1 to ground with a 1000pF capacitor.
Data Filter
The data filter is implemented as a 2nd-order lowpass
Sallen-Key filter. The pole locations are set by the com-
bination of two on-chip resistors and two external
capacitors. Adjusting the value of the external capaci-
tors changes the corner frequency to optimize for dif-
ferent data rates. The corner frequency should be set
to approximately 1.5 times the fastest expected data
rate from the transmitter. Keeping the corner frequency
near the data rate rejects any noise at higher frequen-
cies, resulting in an increase in receiver sensitivity.
The configuration shown in
Figure
2 can create a
Butterworth or Bessel response. The Butterworth filter
offers a very flat amplitude response in the passband
and a rolloff rate of 40dB/decade for the two-pole filter.
The Bessel filter has a linear phase response, which
works well for filtering digital data. To calculate the
value of C5 and C6, use the following equations, along
with the coefficients in
Table
2:
where f
C
is the desired 3dB corner frequency.
For example, to choose a Butterworth filter response
with a corner frequency of 5kHz:
Choosing standard capacitor values changes C5 to
470pF and C6 to 220pF, as shown in the
Typical
Application Circuit
.
Data Slicer
The data slicer takes the analog output of the data filter
and converts it to a digital signal. This is achieved by
using a comparator and comparing the analog input to
a threshold voltage. One input is supplied by the data
Table
2. Coefficents to Calculate C5 and C6
C
k
kHz
pF
C
k
kHz
pF
5
1 000
.
1 414 100
.
(
3 14 5
.
450
6
1 414
3 14 5
.
)(
( )(
225
.
=
)(
)
≈
=
)
≈
C
b
k
a
k
a
f
C
C
C
5
100
(
6
4 100
=
)( )( )
π
=
)( )( )
π
f
C
C
C
C
C
P
M
2
CASE
LOAD
CASE
SPEC
=
+
+
×
1
1
10
6
-
M
315MHz/433MHz ASK Superheterodyne
Receiver with AGC Lock
12
______________________________________________________________________________________
RSSI
R
DF1
100k
R
DF2
100k
C5
19
DFO
21
OPP
22
DFFB
C6
MAX7033
FILTER TYPE
Butterworth (Q = 0.707)
Bessel (Q = 0.577)
a
b
1.414
1.3617
1.000
0.618
Figure
2. Sallen-Key Lowpass Data Filter
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX7033_1 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Evaluation Kit |
| MAX7033_11 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:315MHz/433MHz ASK Superheterodyne Receiver with AGC Lock |
| MAX7033_1109 | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:315MHz/433MHz ASK Superheterodyne Receiver with AGC Lock |
| MAX7033ETJ | 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:315MHz/433MHz ASK Superheterodyne Receiver with AGC Lock |
| MAX7033ETJ+ | 功能描述:射頻接收器 315MHz/433MHz ASK Superheterodyne Rec RoHS:否 制造商:Skyworks Solutions, Inc. 類型:GPS Receiver 封裝 / 箱體:QFN-24 工作頻率:4.092 MHz 工作電源電壓:3.3 V 封裝:Reel |
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