CXA3067M
Function Explanation
The CXA3067M is an integrated circuit designed for CATV wide band FSK receiver. This monolithic IC is
composed of local oscillator, double balanced mixer, limiter, FM detector, data shaper and PLL circuit in a
single chip.
The function of each other section is described below.
1. RFamp circuit
This circuit amplifies RF signal, and RF signal is input to pin 24 (RFIN).
Since pin 27 is an open collector, connect power supply through a coil which composes tune circuit or a
choke coil or a resistor.
RF signal is selected a desired frequency by this tune circuit.
The desired frequency is input to mixer circuit through coupling capacitor.
2. Mixer circuit
This is a double-balanced mixer having small leakage of local signal.
The RF signal is converted to IF signal by the signal supplied from oscillator.
The output impedance is approximately 330 Ω.
Normally, connect a ceramic filter to 10 pin (MIXOUT).
3. Local oscillator circuit
The balanced oscillator circuit with pins 7 and 8 (OSC1, OSC2).
Connect an LC resonance circuit comprising a varicap diode to pins 7 and 8.
4. PLL circuit
The PLL circuit fixes the local oscillator frequency to desired frequency.
It consists of the main divider, reference divider, phase comparator, charge pump, reference oscillator.
As stated in the accompanying document, desired frequency (channel) can be selected through the
combination of the conditions of pins 1, 29 and 30 (FSET 1; 2; 3).
As stated in the accompanying document, reference frequency can be selected through the combination
the conditions of pin 3 (RDSW) and pin 28 (REFSW).
5. Limiter circuit
This circuit amplifies the mixer IF output through ceramic filter.
For quadrature FM detection, this circuit amplifies IF signal by necessary level.
The input impedance is approximately 330 Ω.
6. Detector circuit
For quadrature FM detection, the phase of limiter output (pin 15) is shifted 90° by discriminator as the
output is input to pin 16.
7. Data shaper
This circuit output performs the waveform shaping of the demodulated FSK signal and outputs the resulting
signal as a rectangular wave.
—13—
SONY [ SONY CORPORATION ]
