Document
CXA3050M
NICAM and SMATV RF MODULATOR/PLL
Description Fully synthesized I2C controlled UHF/VHF TV RF Modulator compatible with PAL and NTSC video formats. Features • Minimal adjustment of external components • For use on VHF and UHF TV Frequencies • Video RF carrier frequency programmable in 125kHz steps • Accepts NICAM 6.552MHz QPSK input signal • Accepts FM Stereo input signal • I2C control of: a. Video RF Carrier Frequency b. Sound Carrier Frequency c. Modulation Depth (±2% Typ.) d. FM Deviation (±8% Typ.) e. P/S ratio (±1dB Typ.) f. Nicam output enable to sleep g. Video RF carrier enable to sleep • On chip Regulator 3.1V Block Diagram
Analog GND Analog VCC NICAM-in OSC VCC
24 pin SOP (Plastic)
Structure Bipolar silicon monolithic IC Applications • PAL and NTSC System VCR • Satellite Receiver • Set Top Box • SMATV Recommended Operating Voltages (Ta = 25°C) • Supply voltage VCC 5.0 ± 0.5 V • Supply for VCO Varactor 30 ± 0.5 V • Operating Temperature –10 to +80 °C
RF-OUT
OSC GND
OSC4
OSC1
OSC2
PDout
14 PLL 11
OSC3
24
23
22
21
20
19
18
17
16
15
13
AMP
NICAM MIXER VIDEO MIXER
AMP VCO AMP
TPSG W/C-CLAMP FM-OSC REG PLL OSC PLL I2C-Interface
1
2
3
4
5
6
7
8
9
10
12
Vreg
Digital-VCC
Mod-adj
Digital GND
Audio-Loop filter
Video-in
Audio-in
SCL
Sony reserves the right to change products and specifications without prior notice. This information does not convey any license by any implication or otherwise under any patents or other right. Application circuits shown, if any, are typical examples illustrating the operation of the devices. Sony cannot assume responsibility for any problems arising out of the use of these circuits.
FM-Tank
–1–
SDA
Xtal
NC
EF
E96331A66-ST
Multi-standard RF Modulator
Audio Loop Audio Filter Tank SMATV Nicam in Analog VCC Ground Digital VCC Digital Ground
Audio in NTSC Amp FM Mod PLL B RF Amp Mixer and Adder P/S control NICAM Mixer
Switch
Audio in PAL 62.5kHz
RF Output A B
Modulation depth
Video in video limiter Modulation depth
Video clamp
Buffer ×2
OSC C D A Loop Filter Loop filter B
–2–
divide 8 Memory Latch CCT divide M Phase detector Regulator V Reg
SDA
I2C
divide 25
4MHz OSC
XTAL 4MHz B A 62.5kHz 250kHz
SCL
B
4MHz
CXA3050M
Fig. 1
CXA3050M
Functional Description of RF Modulator System A block diagram of the RF modulator is shown in Fig. 1. The composite video signal passes through an amplitude limiting circuit and a digitally controlled modulation depth adjustment circuit. By means of three allocated I2C control bits it is possible to adjust the modulation depth from a nominal 74% to 86% in 2.0% steps. Modulation depth can also be controlled externally by addition of an external resistor on pin3. The video signal is then passed through to the mixer. In the mixer stage, both the video composite signal and FM sound carrier amplitude modulate the RF carrier from the UHF OSC, and the issuing signal is fed to the output via an RF amplifier. The audio signals enter the chip via pin4. The FM Voltage Controlled Oscillator is band-switched to the approximate centre frequencies of the four sound carrier frequencies 4.5MHz (NTSC) or 5.5, 6.0, 6.5MHz (PAL). The required correct audio carrier frequency is fine tuned by the adjustment of fsound via I2C, where upon the FM phase locked loop will lock the VCO onto the exact centre frequency. Minimum distortion of the FM signal occurs when the centre frequency of the oscillator coincides with a mid-rail control voltage (to 2.0V). Hence fine adjustment capacitors are also integrated on the chip, which tag into account any capacitance variations from one batch to another. This is achieved by fine adjustment of Delta fsound via I2C control. The design of the FM modulator eliminates the need for an external varactor. The amplitude of the FM signal is varied via I2C by a digitally controlled logarithmic gain stage, which controls the picture to sound power ratio (P/S). This signal is then fed into the RF amp. Hence at the RF output the P/S ratio can be programmed in 1dB steps between the range 10dB and 17dB (see Electrical Characteristics). Audio sensitivity can be programmed in 8% steps between the range –32% and +24%. The UHF is phase locked to the reference frequency by means of the UHF phase locked loop. The VCO output passes through a prescaler (≈8) followed by an I2C controlled programmable divider (≈M), and then phase compared with that of a reference signal at 15.625kHz. The reference signal is derived from a 4MHz crystal oscillator feeding a –256 divider. The UHF oscillator covers the frequency range 471MHz to 855MHz in frequency steps of 125kHz. This is adequate for the UHF NTSC and PAL TV channels (471.25MHz (CH21) to 855.25MHz (CH69)). By adjustment of the external components around the oscillator and some adjustment to output matching the RF modulator can also achieve range of frequencies in the VHF range. The Nicam input (pin 22) accepts the 6.522MHz Nicam signal subcarri.