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P
PRELIMINARY INFORMATION
and limited characterization. They may change without notice. Contact Fairchild Semiconductor for current information.
describes products that are not in full production at the time of printing. Specifications are based on design goals
www.fairchildsemi.com
Features
Integrated Analog IF Front-End
Fully differential I/O
IF flat bandwidth from 25 MHz to 55 MHz
48dB minimum gain at IF frequency
Simple interface to SAW filter
9dB input noise figure
Direct interface to A/D converter
More than 50dB IMD3
Industry standard 24-lead SOIC package
Applications
IF sampling decoders
QAM Receivers (up to 256 Constellations)
Set-top receivers for digital cable
Internet surf boards
Cable modems
Desktop video Conferencing
Description
The RC6505 incorporates IF gain stages, reference
generators and a crystal oscillator on a single chip. The high
input impedance enables direct interface to a SAW filter,
while maintaining a low noise figure. The IF output can be
further filtered externally and fed to the on-chip fully
differential buffer/driver. This buffer is extremely useful
when driving low impedance terminations like a differential
input to an A/D. The RC6505 is specially suited in IF
sampling applications for minimizing the parts count and
thus achieving smaller board sizes and lower system costs.
The IF section works on a 12V supply voltage. The oscillator
section runs on 5V supply. The RC6505 is available in a
24 Lead SOIC package.
Block Diagram
VCC_RF
XTL2 XTL1
XOSCOA
RFGND
BUF_OUT-
BUF_OUT+
GND_BUF
VCC_BUF
VRT
INP
OUT
IF_IN-
IF_IN+
VCC_IF2
GND_IF1
IF_OUT+
IF_OUT-
BandGap Ref
OPA
+
-
XTL
OSC
Buffer
Av=1.5
3.25V Ref
400uA Iref
Av=26
Av=10
VCC_IF1
GND_IF2
Translator
BUF_IN-
BUF_IN+
IFA1
IFA2
65-6505-01
RC6505
Differential IF Front-End
Rev. 0.9.1