cxa3095n Sony Electronics, cxa3095n Datasheet - Page 6

• Manufacturer Part Number: cxa3095n
• Description: All Band Tv Tuner Ic Vhf-catv-uhf
• Manufacturer: Sony Electronics

CXA3095N
Description of Operation (See Electrical Characteristics Measurement Circuit.)
VHF oscillator circuit
The differential oscillator circuit with an output at Pin 10 and an input at Pin 12.
Connect an LC resonance circuit comprising a varicap diode to Pin 10 through a coupling capacitor.
The positive feedback from the resonance circuit is applied to Pin 12 through a feedback capacitor to execute
oscillation. Note that if a parasitic capacitance across Pins 10 and 12 is too large, it may cause undesired stray
oscillation.
VHF mixer circuit
This is a common emitter type double-balanced mixer having small leakage of local oscillation signal. The RF
signal is input to Pins 16 and 17. In normal use, the signal is input to one pin while the other pin is connected
to GND by decoupling capacitor. The RF signal is converted to IF frequency with the signal supplied from
oscillator. The converted RF is sent to the IF frequency and output to Pins 20 and 21.
UHF oscillator circuit
UHF oscillator is formed from two collector-grounded Colpitts oscillators, and oscillation is provided at the
differential input through an LC resonator circuit comprising a varicap diode. LC resonator comprising a varicap
diode is connected across Pins 4, 5, 8, and 9.
UHF mixer circuit
The double-balanced mixer like the VHF mixer is adopted. The RF signal is input to Pins 13 and 14. There is a
balanced differential input from pre-stage double tune circuit, or an unbalanced input to Pin 14 with the
capacitor connected at Pin 13 to GND. Otherwise, the conditions and usage are the same as those for the
VHF mixer circuit.
IF amplifier circuit
The frequency converted signal at mixer is output from Pins 20 and 21, and input to IF input pins 23 and 24
through the external IF tune circuit. As an IF tune circuit, single tune circuit like the electrical characteristics
measurement circuit or double tune circuit can be connected. The amplified signal at IF amplifier is output to
Pin 1. The output impedance is approximately 75 .
Also, input block of the IF amplifier has a built-in coupling capacitor, and direct connection with the mixer
output is possible.
UHF/VHF switch circuit
UHF operation is chosen by applying 3V or more voltage to Pin 2; VHF operation for 0V or OPEN.
PLL oscillator signal output circuit
Oscillation signal is output to PLLOUT through buffer amplifier. The resistance connected to the output pin is
for current adjustment flowing to buffer amplifier. The resistance value is adjusted depending on the connected
load, and output distortion can be minimized.
Notes on Usage
Care should be taken such as grounding in placing external parts because high frequencies are present. GND
(Pins 6, 7, 18, and 19) are served both as heat dissipation pins, and adjust accordingly to prevent heat
problems.
Please concern for damage by static electricity for high frequency input/output pins.
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