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RC6508 PDF даташит

Спецификация RC6508 изготовлена ​​​​«Raytheon» и имеет функцию, называемую «QAM IF Downconverter».

Детали детали

Номер произв RC6508
Описание QAM IF Downconverter
Производители Raytheon
логотип Raytheon логотип 

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RC6508 Даташит, Описание, Даташиты
RC6508
QAM IF Downconverter
Electronics
Semiconductor Division
Features
• Integrated IF Down Converter
• IF bandwidth from 30 MHz to 80 MHz
• Operating range between 8.5V to 13.2V
• 63dB peak conversion gain from IF to baseband
• 40dB minimum AGC range
• Simple interface to SAW filter and A/D converter
• Gain control minimizes noise figure and distortion
• Tuner control feature interfaces with variety of tuners
• Industry standard 24 Lead SSOP package
Applications
• Digital Set-top Receivers
• Cable Modems
Description
The RC6508 simplifies the front-end design of cable modem
and set-top receivers. It is a cost-effective solution, since it
integrates IF amplifier, AGC, mixer, amplifier, tuner AGC,
VCO, XTAL OSC, and bandgap reference on a single chip.
The RC6508 downconverts the IF signal to baseband signal
for cable modem and set top receivers. The baseband signal
can be digitized and decoded with an external A/D converter
and a custom DSP demodulator. The input can directly inter-
face to a SAW filter and maintain a low noise figure. The gain
can be controlled over a 40dB range through an external
analog input signal. The gain reduction is done in two stages
with minimum noise figure and signal distortion. The IF out-
put is then down converted and filtered using a double bal-
anced mixer. The output can be further filtered with an
external filter prior to A/D conversion. The RC6508 has an
added feature that it provides an optimum tuner AGC control
voltage which is used to control the front end tuner gain.
The IF and Mixer section works at 9V and the oscillator
works on 5V supply. The RC6508 is available in a 24 Lead
SSOP package.
Block Diagram
VCC_HF
HFGND
IF_IN+
IF_IN–
IF_AGC
T_Strt
T_AGC
45dB
x2
+
VCC_RF (5V)
BB_GND
VCC_BB BB_Out
RF BB
LO
17dB
VCO
XTAL Osc
BANDGAP
REF
65-6508-01
Rev. 1.1.1









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RC6508 Даташит, Описание, Даташиты
RC6508
PRODUCT SPECIFICATION
Functional Description
The RC6508 shown in the block diagram performs all the IF
and baseband signal conversion with the minimal external
components. It consists of three general sections:
• IF Gain Section
• IF Down Conversion and Frequency Synthesis
• Reference Voltage
IF Gain Section
This is the first stage of the IF-to-Baseband conversion. The
IF input signal is fed into a variable gain control amplifier
that is capacitively coupled to the subsequent stages. The
gain control amplifier has stabilized gain over temperature
and supply variations. The amplifier gain is directly propor-
tional to the IF_AGC voltage. The gain in various stages is
not reduced at the same time in order to minimize the noise
figure degradation. The transition point is set by the voltage
on T_Strt pin. T_strt sets the T_AGC trigger to control the
front end tuner gain.
IF Down Conversion and Frequency Synthesis
This is the second stage of the IF-to-Baseband conversion. It
consists of a double balanced linear mixer. The output of the
front end gain stage is capacitively coupled to the input (RF
port) of the mixer. The LO signal for the mixer can be
directly driven or synthesized with the Voltage Controlled
Oscillator (VCO). This section has also a crystal oscillator
that can be used to generate a master clock for the frequency
synthesis. The mixer translates the signal to a second IF fre-
quency equal to the symbol rate and passes through an
amplifier. The final output is a baseband signal, BB_Out.
This signal can be further filtered externally before connect-
ing it to an external ADC and QAM demodulator.
Reference Voltage
The RC6508 has a built-in 2.0V reference with capability of
driving 10mA load and can be used to set up A/D reference.
Pin Assignments
VCC_XTL
GND_XTL
XTL_Tnk
XTL_Out
RFGND
VCC_RF
VCO_In
VCO_Fs
BB_GND
NC
BB_Out
VCC_BB
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
65-6508-02
T_Strt
IF_AGC
T_AGC
VCC_HF
HFGND
IF_IN–
IF_IN+
SGND
NC
VCC2
VRT
NC
2









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RC6508 Даташит, Описание, Даташиты
PRODUCT SPECIFICATION
RC6508
Pin Descriptions
Pin Name
BB_GND
BB_Out
GND_XTL
HFGND
IF_AGC
IF_IN+,IF_IN–
NC
RFGND
SGND
T_AGC
T_Strt
VCC_BB
VCC2
VCC_HF
VCC_RF
VCC_XTL
VCO_Fs
VCO_In
VRT
XTL_Out
XTL_Tnk
Pin Number
9
11
2
20
23
18,19
10,13,16
5
17
22
24
12
15
21
6
1
8
7
14
4
3
Pin Function Description
Ground Connection.
Baseband Voltage output.
Crystal Oscillator Ground.
Analog Ground Connection.
Input Voltage for IF Front End Gain Control.
IF inputs.
No Connection.
Ground Connection for High Frequency Mixed Signal Sections.
Analog Ground Connection.
Output Voltage for Tuner Gain Control.
Threshold Voltage Input for Starting Tuner Gain Control.
Baseband Supply Voltage, typically 9V.
Analog Supply Voltage (9V).
Analog Supply Voltage (9V).
Supply Voltage (5V) for High Frequency Mixed Signal Sections.
Supply Voltage for Crystal Oscillator.
VCO External Frequency Select Circuit Connection.
VCO Input, can be used for directly feeding external LO.
Output reference voltage for top of A/D input range.
Crystal Oscillator Output.
Crystal Oscillator Frequency Select Circuit Connection.
Absolute Maximum Ratings
Parameter
IF_IN+, IF_IN–,
IF_AGC, T_Strt
VCC_RF, VCC_BB,
VCC_HF, VCC2,
VCC_XTL
Tstg
Input Voltages
Analog Supply Voltages
Storage Temperature
Min.
GND – 0.3
-40
Typ.
Max.
VCC + 0.3
13.5
Units
V
V
125 °C
Operating Conditions
Parameter
VCC
VCC_RF
VCC_XTL
T
Analog Supply Voltage
Supply Voltage for IF and
Mixer
Supply Voltage for
XTLOSC and VCO
Temperature
Min.
8.5
4.75
0
Typ.
9
5
Max.
13.2
5.25
Units
V
V
70 °C
3










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