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RC6564
PRODUCT SPECIFICATION
2
P
Functional Description
The RC6564 performs all the IF and baseband signal pro-
cessing/conversion with the help of external filters. As shown
in the Block Diagram, the RC6564 consists of three general
sections:
1.
2.
3.
IF Gain blocks with Gain Control
IF down conversion with LO & Clock Generation
Analog to Digital Conversion
The IF Section:
The signal input is into a variable gain
amplifier capacitively coupled to the subsequent stages.
When the voltage on IF_AGC pin is higher, the gain is
higher and when it is lower the gain is lower too. To mini-
mize the noise figure degradation with gain reduction the
gains in various stages are not reduced simultaneously. The
transition point is set by the voltage on T_Strt pin. When the
IF_AGC voltage is higher than half the T_Strt voltage the
gain reduction rate is steepest. When the IF_AGC voltage is
lower than roughly half the T_Strt voltage the gain reduction
is at a slower rate. The T_AGC output voltage also changes
and can be used to gain reduce the front-end tuner. The gain
control amplifier has stabilized gain over temperature and
supply variations.
IF Down Conversion & Frequency Synthesis:
This section
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 mixer output is further amplified. The
signals for the Local Oscillator (LO) port of the mixer can be
directly driven or synthesized through the VCO (Voltage
Controlled Oscillator). The mixer output is partially filtered
on-chip but may need to be further filtered externally before
being fed to the A/D input. The RC6564 also has a crystal
oscillator circuit that can be used for generating a master
clock for frequency synthesis.
Analog-to-Digital Converter:
The analog-to-digital con-
verter employs a two-step 9-bit architecture to convert ana-
log signals into digital words at sample rates up to 40 Msps
(Mega samples per second). An integral Track/Hold circuit
delivers excellent performance on signals with full-scale
components up to 12MHz. A dynamic performance of more
than 7.4 effective bits is delivered at the outputs D0 through
D7. The A/D digital outputs are three-state and TTL/CMOS
compatible. The down converted output at BB_OUT can be
externally filtered and directly connected to the A/D input.
Sampling of the applied input signals takes place on the fall-
ing edge of the AD_CLK. The output word is delayed by 2.5
AD_CLK cycles. An output enable control OE places the
outputs in high impedance state when HIGH. The outputs
are enabled when OE is LOW as described in the Timing
Diagrams section.
Block Diagram
VCC_HF
HFGND
V
R
R
R
V
V
V
S
V
A
V
X
X
G
B
V
B
A
IF_IN+
RF
LP FILTER
BB
LO
4.6dB
17dB
65-6564-02
VCO
x2
IF_IN–
IF_AGC
T_Strt
T_AGC
T/H
D0-D7
OE
–
+
V
A
V
D
XTAL Osc
BANDGAP
REF
VREF
MATRIX
FINE
A/D
COARSE
A/D
D