CXA3018R 查看數據表（PDF） - Sony Semiconductor

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CXA3018R

Demodulator for Satellite Receivers

Sony Semiconductor 

CXA3018R

(4) CLAMP & VAMP blocks of video signal processor

The signal input from VAMPIN is sync-tip clamped by CLAMP1 and input to the VAMP block. VAMP selects

NTSC or PAL gain according to the NTSC/PAL switching commands from the LOGIC block. The gain is

output from Pin 16 after being amplified to the proper level (1 Vp-p for sync tip to 100 % WHITE). The Pin 16

output signal is input to CLAMP2 from Pin 15 where it is sync-tip clamped again. CLAMP1 & 2 are enabled

by the CLAMP pulse which is input to Pin 14. The CLAMP1 & 2 blocks eliminate the triangular wave

components (15 to 30 Hz) which overlap with the video signal for the energy diffusing signal. The final video

signal is output from Pin 13.

(5) AFT block

This block detects frequency error in the 2nd IF signal as a voltage displacement from the FM demodulation

signal which is input to the AFT block, and outputs the two values of High (5 V) or Low (0 V) from Pins 1 and

2. High indicates the frequency change command (active-High). Furthermore, High output from both pins

indicates the dead zone. Connecting an LPF capacitor to Pin 3, applying the reference voltage to Pin 4, and

connecting a resistor between Pins 3 and 4 changes the AFTAMP gain, thereby allowing the dead zone

width to be changed. Input the keyed pulse for keyed AFT to Pin 5. The Pin 5 voltage should be 0 V during

mean value AFT. Connect sample-and-hold capacitors to Pins 6 and 7. Apply the offset adjustment voltage

to Pin 46 to cancel the effects of the DC offset inside the IC.

(6) C/N detection block

Extract the noise component from the DETOUT signal output from Pin 42 with an external BPF and input it to

the C/N detection block from Pin 8. Output the C/N conversion output from Pin 11. Apply the C/N detection

adjustment voltage to Pin 9, connect an LPF capacitor to Pin 10, and connect a decoupling capacitor for the

voltage source for correcting temperature characteristics to Pin 12.

(7) Other

Connect a capacitor to cancel the regulator voltage noise to Pin 48, and use this output as the reference

voltage for internal adjustment.

—12—

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