CXA3185/3186N
Description of Functions
The CXA3185/3186N is a terrestrial wave broadcast tuner IC which converts frequencies to IF in order to
tune and detect only the desired reception frequency of VHF, CATV and UHF band signals.
In addition to the mixer, local oscillator and IF amplifier circuits required for frequency conversion to IF, this
IC also integrates a PLL circuit for local oscillator frequency control onto a single chip.
The functions of the various circuits are described below.
1. Mixer circuit
This circuit outputs the frequency difference between the signal input to VHFIN or UHFIN and the local
oscillation signal.
2. Local oscillator circuit
A VCO is formed by externally connecting an LC resonance circuit composed of a varicap diode and
inductance.
3. IF amplifier circuit
This circuit amplifies the mixer IF output, and consists of an amplifier stage and low impedance output
stage.
4. PLL circuit
This PLL circuit fixes the local oscillator frequency to the desired frequency. It consists of a prescaler, main
divider, reference divider, phase comparator, charge pump and reference oscillator. The control format
supports the 3-wire bus format. The following four modes can be selected according to the combination of
the frequency division values of the main and reference dividers.
Mode
A-0
Main divider
15 bit
Reference divider
1024 fixed
512 fixed
A-1
14 bit
A-2
15 bit
640 fixed
A-3/4
15 bit
512 fixed
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SONY [ SONY CORPORATION ]
