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.

www.fairchildsemi.com

Features

• 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

Applications

• Digital Set-top receivers

• Cable modems

• Internet surfboards

• Network Interface Modules

• Multimedia PCs

Description

The RC2798 is an integrated solution for the down-

conversion 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.

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.

Block Diagram

1

AGC_IN1

2

AGC_IN2

3

VAGC

4

VCC MIX

5

OSC_OUT

6

GND

7

B2

8

C1

9

C2

10

20

19

18

17

16

15

14

13

12

11

B1

GND

MIX_OUT2

MIX_OUT1

G1A

G1B

VampIn1

VampIn2

VccAmp

VideoAmp

LO

AGC + MIX

RC2798

OUT1

OUT2

RC2798

Integrated QAM IF Downconverter

Rev 1.0.0