www.fairchildsemi.com
RC2798
Integrated QAM IF Downconverter
Features
Description
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The RC2798 is an integrated solution for the downconversion of QAM IF signals in the front-end design of
cable modem and set-top receivers. It is intended for use in
64QAM and 256QAM IF downconversion applications.
The RC2798 integrates IF amplifier with AGC , mixer, VCO,
and a video amplifier on a single chip. It accepts the QAM IF
signals via SAW filter and downconverts it to 5MHz
baseband signal.
RF input frequency range 30 to 250MHz
On chip VCO with LO frequency range 30 to 250MHz
IF amplifier with AGC setting
High dynamic range -9dBm IIP3
On chip Video Amplifier
Built in ESD protection
Supply voltage range 5 to 10 V
Space saving 20-Lead TSSOP package
The baseband signal can be digitized using Fairchild
Semiconductor’s 8 bit A/D (TMC1175 series) or 10bit A/D
(TMC1185 series) and decoded further with a QAM
demodulator. The IF, Oscillator and Mixer section work at
5V. The video amplifier works at 5V to 10V. The RC2798 is
available in a 20 Lead TSSOP package.
Applications
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Digital Set-top receivers
Cable modems
Internet surfboards
Network Interface Modules
Multimedia PCs
Block Diagram
RC2798
20 GND
AGC_IN1
1
AGC_IN2
2
VAGC
3
18 MIX_OUT1
VCC MIX
4
17 G1A
OSC_OUT
5
16 G1B
GND
6
19 MIX_OUT2
AGC + MIX
15 VampIn1
LO
B2
7
14 VampIn2
C1
8
13 VccAmp
C2
9
12 OUT1
VideoAmp
B1 10
11 OUT2
Rev 1.0.0
PRELIMINARY INFORMATION describes products that are not in full production at the time of printing. Specifications are based on design goals
and limited characterization. They may change without notice. Contact Fairchild Semiconductor for current information.