STV2246C datasheet(17/76 Pages) STMICROELECTRONICS

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STV223XD/224XC - FUNCTIONAL DESCRIPTION

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3 FUNCTIONAL DESCRIPTION

The STV2238D is an integrated device that proc-

esses PIF, SIF, Video and Chroma signals while

scanning for PAL, SECAM and NTSC standards. It

includes a base band chroma delay line, Video,

SVHS and audio switches.

3.1 DETAILED FEATURES

3.1.1 Power Supplies

VCCIF: 5 V power supply dedicated to IF proces-

sors.

VCCD: 5 V power supply dedicated to I²C bus and

digital parts. GNDD is the ground reference of

these parts.

VCC1: 8 V power supply for video switches, scan-

ning part and the chroma decoder. GND 1 is the

ground reference of all these functions.

VCC2: 8 V power supply for the luminance, RGB

processing parts audio switch and internal CVBS

output. GND2 is the ground reference of these

parts.

3.1.2 Picture Intermediate Frequency (PIF)

– AGC amplifier.

– PLL synchronous demodulator. Bus-controlled

VCO for integrated tuning of the external LC res-

onator. For a 38.9 MHz VCO, the LC coil specifi-

cation has to be:

C = 39pF, f = 44 MHz ±2% (LC not connected).

For a 33.9 MHz VCO (L’), the VCO can be

switched via the bus control.

– Digital AFC via bus.

– IF Automatic Gain Control (AGC)

Negative modulation: top sync regulation, regu-

lation of overmodulated signals (overmodulation

regulation circuit enabled through bus control).

Positive modulation: main regulation on white

level with black level limitation.

– Tuner-delayed AGC with bus control for AGC

gain and threshold. When tuner AGC output is

active, read register 03hex, data D7 is set to “1”.

– CVBS output with 2 bus-controlled amplitudes.

CVBS output at 2 VPP if external sound trap is

not connected (QSS mode). CVBS output at 2.3

VPP if external sound trap is connected (Intercar-

rier mode).

3.1.3 Sound Intermediate Frequency (SIF) and

Sound Demodulators

– QSS structure.

– SIF Automatic Gain Control (QSS mode).

– Built-in sound bandpass.

– PLL FM Demodulator for 4.5, 5.5, 6.0 or 6.5 MHz

carriers. The Sound Standard is selected by the

MCU. The FM demodulator VCO is automatically

calibrated using the chroma crystal VCO refer-

ence frequency. The FM Demodulator VCO is

automatically calibrated for all sound standards

independently of the chroma crystal VCO fre-

quency, which is either 4.4 MHz or 3.5 MHz. For

each sound carrier frequency, the IC sends an

indication of the sound subcarrier level to the

MCU so that it can select the proper standard.

– The sound subcarrier level is valid when the FM

Demodulation VCO is calibrated. This informa-

tion can be read via the I²C Bus.

– Bus controls for FM de-emphasis (50 or 75 µs)

and FM deviation ±25 or ±50 kHz).

– AM demodulator.

– Sound demodulator output: either an AM or FM

signal can be the output for the Mono chassis

– Sound subcarriers for the Stereo chassis.

3.1.4 Audio Switch

– One SCART switch.

– Bus-controlled volume and mute. Zero-crossing

function on volume control.

– Automatic Volume Levelling (AVL) function can

be enabled via the I²C bus. Two time constants

(gain increase) can be selected via the I²C bus.

– The AM sound can be selected on the main au-

dio output for the Stereo chassis.

3.1.5 Surface Acoustic Wave (SAW) Filter

Switch Control

– SAW filter switch control pin is available in the

TQFP64 package. The SAW filter switch control

pin is used to select the correct SAW filter char-

acteristics (e.g.: M/N or BGDK characteristics).

In a multi-standard chassis, two output voltages

are selected via the I²C bus (low level voltage at

0.4 V Max., and high level voltage at 4 V Min.).

3.1.6 Video Switches

– Video switch with three CVBS inputs and one

CVBS output (CVBSOUT1) which may be used

to drive a teletext decoder.

– A second CVBS output (CVBSOUT2) is able to

output recombined Y+C signals.

All switches are independently controlled.

– SVHS switch, Y input is combined with CVBS 3

input. CVBS/SVHS modes can be selected ei-

ther by bus control (software selection), or by

sensing the DC voltage on the Chroma Input pin

(hardware selection). If the Chroma Input is

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