TDA4681 Datasheet, PDF (2/28 Pages) NXP Semiconductors – Video processor with automatic cut-off and white level control

Philips Semiconductors
Video processor with automatic cut-off
and white level control
Product specification
TDA4681
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 fully-controlled, analog RGB inputs, selected either
by fast switch signals or via I²C-bus
• Saturation, contrast and brightness 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, horizontal and vertical
synchronization, cut-off and white level timing pulses
• Automatic cut-off control with picture tube leakage
current compensation
• Software-based automatic white level control or fixed
white levels via I²C-bus
• Cut-off and white level measurement pulses in the last
4 lines of the vertical blanking interval (I²C-bus selection
for PAL, SECAM, or NTSC, PAL-M)
• Increased RGB signal bandwidths for progressive scan
and 100 Hz operation (selected via I²C-bus)
• 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
• Three adjustable reference voltage levels (via I²C-bus)
for automatic cut-off and white level control
• Emitter-follower RGB output stages to drive the video
output stages
• Hue control output for the TDA4555, TDA4650/T,
TDA4655/T or TDA4657.
GENERAL DESCRIPTION
The TDA4681 is a monolithic integrated circuit with a
colour difference interface for video processing in TV
receivers. Its primary function is to process the luminance
and colour difference signals from multistandard colour
decoders, TDA4555, TDA4650/T, TDA4655/T or
TDA4657, Colour Transient Improvement (CTI) IC,
TDA4565, Picture Signal Improvement (PSI) IC, TDA4670
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; both inputs are
fully-controlled internally. The TDA4681 includes full
I²C-bus control of all parameters and functions with
automatic cut-off and white level control of the picture tube
cathode currents. It provides RGB output signals for the
video output stages.
There is a very similar IC available, TDA4680. The only
differences are in the NTSC matrix.
ORDERING INFORMATION
TYPE NUMBER
TDA4681
TDA4681WP
NAME
DIP28
PLCC28
PACKAGE
DESCRIPTION
plastic dual in-line package; 28 leads (600 mil)
plastic leaded chip carrier; 28 leads
VERSION
SOT117-1
SOT261-2
1997 Mar 04
2