參數(shù)資料
型號: ATA5744N-TGQY
廠商: ATMEL CORP
元件分類: 通信及網(wǎng)絡(luò)
英文描述: SPECIALTY TELECOM CIRCUIT, PDSO20
封裝: LEAD FREE, SO-20
文件頁數(shù): 14/20頁
文件大小: 316K
代理商: ATA5744N-TGQY
3
4893A–RKE–11/05
ATA5744
Figure 2-2.
Block Diagram
3.
RF Front End
The RF front end of the receiver is a heterodyne configuration that converts the input signal into
a 1-MHz IF signal. According to Figure 2-2, the front end consists of an LNA (Low-Noise Ampli-
fier), LO (Local Oscillator), a mixer and RF amplifier.
The LO generates the carrier frequency for the mixer via a PLL synthesizer. The XTO (crystal
oscillator) generates the reference frequency f
XTO. The VCO (Voltage-Controlled Oscillator) gen-
erates the drive voltage frequency f
LO for the mixer. fLO is dependent on the voltage at pin LF. fLO
is divided by factor 64. The divided frequency is compared to f
XTO by the phase frequency detec-
tor. The current output of the phase frequency detector is connected to a passive loop filter and
thereby generates the control voltage VLF for the VCO. By means of that configuration, VLF is
controlled in a way that f
LO/64 is equal to fXTO. If fLO is determined, fXTO can be calculated using
the following formula:
f
XTO = fLO/64
The XTO is a one-pin oscillator that operates at the series resonance of the quartz crystal.
According to Figure 3-1, the crystal should be connected to GND via a capacitor CL. The value
of that capacitor is recommended by the crystal supplier. The value of CL should be optimized
for the individual board layout to achieve the exact value of f
XTO and hereby of fLO. When design-
ing the system in terms of receiving bandwidth, the accuracy of the crystal and the XTO must be
considered.
ASK-
Demodulator
and data filter
RSSI IF Amp
IF Amp
4. Order
LPF
3 MHz
LPF
3 MHz
Dem_out
RSSI
Standby logic
VCO
XTO
64
f
CDEM
AVCC
RSSI
AGND
DGND
MIXVCC
LNAGND
LNA_IN
DATA
ENABLE
TEST
MODE
LFGND
LFVCC
XTO
LF
DVCC
LNA
Data interface
Test
BR_0
BR_1
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ATA5744N-TKQY 功能描述:射頻接收器 ASK Remote Control Rec. 433 MHz 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
ATA5744N-TKQY 19 功能描述:射頻接收器 RF DATA CONTROL RECEIVER 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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ATA5744N-TKSY 19 功能描述:射頻接收器 RF DATA CONTROL RECEIVER 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