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TDA4686

Video processor with automatic cut-off control

Philips Electronics 

Philips Semiconductors

Video processor with automatic cut-off control

Product specification

TDA4686

FEATURES

• Intended for double line frequency application

(100/120 Hz)

• Operates from an 8 V DC supply

• Black level clamping of the colour difference, luminance

and RGB input signals with coupling-capacitor DC level

storage

• Two analog RGB inputs, selected either by fast switch

signals or via I2C-bus; brightness and contrast control of

both RGB inputs

• Saturation, contrast, brightness and white adjustment

via I2C-bus

• Same RGB output black levels for Y/CD and RGB input

signals

• Timing pulse generation from either a 2 or 3-level

sandcastle pulse for clamping, vertical synchronization

and cut-off timing pulses

• Automatic cut-off control or clamped output selectable

via I2C-bus

• Automatic cut-off control with picture tube leakage

current compensation

• Cut-off measurement pulses after end of the vertical

blanking pulse or end of an extra vertical flyback pulse

• Increased RGB signal bandwidths

• Two switch-on delays to prevent discolouration before

steady-state operation

• Average beam current and peak drive limiting

• PAL/SECAM or NTSC matrix selection via I2C-bus

• Emitter-follower RGB output stages to drive the video

output stages

• I2C-bus controlled DC output e.g. for hue-adjust of

NTSC (multistandard) decoders

• No delay of clamping pulse

• Large luminance, colour difference and RGB bandwidth.

GENERAL DESCRIPTION

The TDA4686 is a monolithic integrated circuit with a

luminance and a colour difference interface for video

processing in TV receivers. Its primary function is to

process the luminance and colour difference signals from

a colour decoder which is equipped e.g. with the

multistandard decoder TDA4655 or TDA9160 plus delay

line TDA4661 and the Picture Signal Improvement (PSI)

IC, TDA467X, or from a feature module.

The required input signals are:

• Luminance and negative colour difference signals

• 2 or 3-level sandcastle pulse for internal timing pulse

generation

• I2C-bus data and clock signals for microcontroller

control.

Two sets of analog RGB colour signals can also be

inserted, e.g. one from a peritelevision connector and the

other from an on-screen display generator. The TDA4686

includes full I2C-bus control of all parameters and

functions with automatic cut-off control of the picture tube

cathode currents. It provides RGB output signals for the

video output stages.

The TDA4686 is a simplified, pin compatible (except for

pin 18) version of the TDA4680. The module address via

I2C-bus can be used for both ICs; where a function is not

included in the TDA4686 the I2C-bus command is not

executed. The differences with the TDA4680 are:

• No automatic white level control; the white levels are

determined directly by the I2C-bus data

• RGB reference levels for automatic cut-off control are

not adjustable via I2C-bus

• No clamping delay

• Only contrast and brightness adjust for the RGB input

signals

• The measurement lines are triggered either by the

trailing edge of the vertical component of the sandcastle

pulse or by the trailing edge of an optional external

vertical flyback pulse (on pin 18), according to which

occurs first.

The TDA4685 is like TDA4686 but intended for normal line

frequency application.

1997 Jun 23

2

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