cxa3250an Sony Electronics, cxa3250an Datasheet - Page 17

• Manufacturer Part Number: cxa3250an
• Description: All Band Tv Tuner Ic With On-chip Pll
• Manufacturer: Sony Electronics

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. Pin 18 is the output and Pin 16 is the input.
• The amplifier between Pins 16 and 18 has an extremely high gain. Therefore, care should be taken to
• The mixer circuit employs a double balanced mixer with little local oscillation signal leakage.
• The RF signal is fed from the oscillator, converted to IF frequency and output from Pins 9 and 10.
• This oscillator circuit is designed so that two collector ground type Colpitts oscillators perform differential
• Resonance capacitance is connected between Pins 19 and 20, Pins 20 and 21, and Pins 21 and 22, and
• This circuit employs a double balanced mixer like the VHF mixer circuit.
• Pins 9 and 10 are the mixer outputs.
• 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.
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 via a capacitor and the RF signal input to Pin
13. (Pin 12 can also be used to switch the PLL mode according to the applied DC voltage value.)
oscillation operation via an LC resonance circuit including a varicap.
an LC resonance circuit including a varicap is connected between Pins 19 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.
AC coupled inside the IC and input to the IF amplifier.
the IF amplifier.
The output impedance is approximately 75 .
—17—
(See the Electrical Characteristics Measurement Circuit.)
CXA3250AN