CXA3235 Sony Corporation, CXA3235 Datasheet - Page 10

• Manufacturer Part Number: CXA3235
• Description: All Band TV Tuner IC with On-chip PLL
• Manufacturer: Sony Corporation

Description of Analog Block Operation
VHF oscillator circuit
VHF mixer circuit
UHF oscillator circuit
UHF mixer circuit
IF amplifier circuit
• This circuit is a differential amplifier type oscillator circuit.
• The amplifier between Pins 16 and 18 has an extremely high gain. Therefore, care should be taken to
• The mixer circuit employs a double balance mixer with little local oscillation signal leakage.
• The RF signal is inserted from the oscillator, converted to IF frequency and output from Pins 9 and 10.
• Pins 9 and 10 are open collectors, so power must be supplied externally. The electric potential of Pins 9
• This oscillator circuit is designed so that two collector ground type Colpitts oscillators perform differential
• Then, LC resonance circuit comprising a varicap diode is connected across Pins 19 and 22.
• This circuit employs a double balance mixer like the VHF mixer circuit.
• Pins 9 and 10 are the mixer outputs.
• Pins 9 and 10 are open collectors, so power must be supplied externally. The electric potential of Pins 9
• The signals frequency converted by the mixer are output from Pins 9 and 10, and at the same time are
• Single-tuned filters are connected to Pins 9 and 10 in order to improve the interference characteristics of
• The signal amplified by the IF amplifier is output from Pin 25.
Pin 18 is the output and Pin 16 is the input.
Oscillation is performed by connecting an LC resonance circuit including a varicap to Pin 18 via coupled
capacitance, inputting to Pin 16 with feedback capacitance, and applying positive feedback.
avoid creating parasitic capacitance, resistance or other feedback loops as this may produce abnormal
oscillation.
The input format is base input type, with Pin 12 grounded and the RF signal input to Pin 13.
and 10 at this time must be DC 4.0 V or more.
oscillation operation via an LC resonance circuit including a varicap. Connect resonator capacitance
composing colpitts oscillators between Pins 19 and 20, Pins 20 and 21, and Pins 21 and 22.
The input format is base input type, with Pins 14 and 15 as the RF input pins. The input method can be
selected from balanced input consisting of differential input to Pins 14 and 15 or unbalanced input
consisting of grounding Pin 14 via a capacitor and input to Pin 15.
and 10 at this time must be DC 4.0 V or more.
AC coupled inside the IC and input to the IF amplifier.
the IF amplifier.
The output impedance is approximately 75 Ω.
—10—
(See the Electrical Characteristics Measurement Circuit.)
CXA3235/3236N