Sony CXA3050M Datasheet

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

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

CXA3050M

24 pin SOP (Plastic)

CC

CC

Analog GND

NICAM-in

NICAM
MIXER

VIDEO
MIXER

FM-OSC

3

Mod-adj

Analog V

21

4

Audio-in

20

RF-OUT

23

24

AMP

W/C-CLAMP

1

Video-in

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.

22

2

Vreg

OSC V

AMP
AMP

PLL

5

FM-Tank

OSC4

19

18

TPSG

6

7

filter

Audio-Loop

OSC3

17

VCO

OSCREG

Digital GND

OSC2

8

Xtal

OSC1

16

9

CC

Digital-V

OSC GND

15

2

I

10

SCL

14

C-Interface

11

PDout

PLL

PLL

SDA

EF

13

12

NC

– 1 –

E96331A66-ST

Ground

A

RF Output

CXA3050M

B

C

A

D

B

Loop filter

XTAL

4MHz

Digital

Analog Digital

SMATV

Audio

Loop

Audio

CC

V

VCC Ground

Nicam in

Tank

Filter

NICAM

Mixer

P/S

control

PLL

FM Mod

RF Amp

and

Mixer

B62.5kHz

Adder

OSC

× 2

Buffer

depth

Modulation

8

divide

Loop

Filter

OSC

4MHz

25

divide

Phase

detector

M

divide

A

B

250kHz

62.5kHz

Regulator

Fig. 1

V Reg

Switch Amp

Audio in

NTSC

Multi-standard RF Modulator

Audio in

PAL

Modulation

depth

video

limiter

Video

clamp

Video in

– 2 –

Memory

2

SDA

CCT

Latch

C
I

B 4MHz

SCL

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 subcarrier QPSK at 728K bits/s data. This is
then buffered and feed into a separate mixer (controlled via VCO). This then feeds to the RF amp with the
composite video and audio. The I2C control will switch the Nicam signal output off or on.

– 3 –

I2C Interface Data Format

CXA3050M

Modulator Address

Data 1
Data 2

Data 3
Data 4

1100100R/Wask

PD

M12

M4

X

Sound Carrier Course Adjust

S1

0
0
1
1

S0

0
1
0
1

Sound Carrier
Frequency

4.5MHz

5.5MHz

6.0MHz

6.5MHz

Sound Carrier Fine Adjust

ADJ1

M11

M3

NIC

TV System
(Pre-emphasis)

ADJ0

M10

M2

FM2

NTSC

PAL
PAL
PAL

S1

M9
M1

FM1

S0

M8
M0

FM0

over
mod

M7

MD2

PS2

X

M6

MD1

PS1

X

M5

MD0

PS0

ask
ask

ask
ask

ADJ1

0
0
1
1

ADJ0

0
1
0
1

df Adjust

–f

Normal

+f
+f

on chip
capacitance

6.4pF

3.2pF

1.6pF
0

PD RF Power on (RF Amp & OSC) 1 bit
OVM Over Modulation Test 1 bit
M12–MO Main divider control data 13 bits
S1–S0 Sound carrier frequency selection 2 bits
ADJ1–ADJ0 Sound carrier frequency adjust (0 to 6.4RF) 2 bits
MD2–MD0 Modulation Depth 3 bits
PS2–PS0 Picture/Sound control 3 bits
FM FM deviation adjust 3 bits
NIC Nicam Enable 1 bit
M12 MO Main UHF PLL Divider
MSB LSB 8191 to 2
Video Carrier frequency calculated from = 125 (M + 2) kHz

– 4 –

CXA3050M

Software Application Notes

The minimum requirement to drive the CXA3050 and I2C bus drive is a 386/486 with 4M bytes hard disk
space, 16MHz clock speed and running DOS5.00 or above. Insert the disc into the drive and type TESTS and
at the prompt type iic. At this there should appear a single list of user friendly functional tests that can be
changed by keyboard manipulation. As an aid the test list is written below. Note Page up increments the
status, page down decrements the status.

Function Nominal Status
RF Output Power
Delta Sound

Fsound

Frequency mode

Mod depth
FM Deviation

P/S Ratio
Nicam on/off
Over Mod on/off

1/0

1

0

2 to 8191

4
4

4
1/0
1/0

Comments

Turns RF Amp, OSC on/off
Fine tune audio carrier
Course adjust for

4.5MHz (0)

5.5MHz (1)

6.0MHz (2)

6.5MHz (3)
Check listing on page 10 for

frequency to hex conversation
Ranges mod depth from

72% to 86%, 80% (4)
Sensitivity adjustable
Programmable in 8 steps of 1dB
Nicam Mixer on
Increase Video modulation ratio

– 5 –

Pin Description

CXA3050M

Pin
No.

1

2

Reference

Video-in

Vreg

Pin Voltage
Typical DC

2.5V

3.1V

Equivalent circuit Description

Vcc

1

Vcc

2

Video input

Chip voltage supply
regulator

3

4

Mod-Adj

Audio-in

2.5V

10mA

MIXER

3

FMOSC

External Adjust Mod
depth.

Audio input

4

5

FM-Tank

4.0V

5

Sound Carrier
oscillator tank

– 6 –