TDA4685 Datasheet, PDF (2/24 Pages) NXP Semiconductors – Video processor with automatic cut-off control

Philips Semiconductors
Video processor with automatic cut-off control
Product specification
TDA4685
FEATURES
• 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
• 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.
GENERAL DESCRIPTION
The TDA4685 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 TDA4685
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 TDA4685 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 TDA4685 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
• Clamping delay is fixed
• 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 TDA4686 is like TDA4685 but intended for double line
frequency application.
ORDERING INFORMATION
TYPE NUMBER
TDA4685
NAME
DIP28
PACKAGE
DESCRIPTION
plastic dual in-line package; 28 leads (600 mil)
VERSION
SOT117-1
1997 Jun 20
2