Electronic Components Datasheet Search
Selected language     English  ▼


TDA4885 Datasheet(PDF) 7 Page - NXP Semiconductors

Part No. TDA4885
Description  150 MHz video controller with I2C-bus
Download  56 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  PHILIPS [NXP Semiconductors]
Homepage  http://www.nxp.com
Logo 

 7 page
background image
1997 Nov 25
7
Philips Semiconductors
Product specification
150 MHz video controller with I2C-bus
TDA4885
7
FUNCTIONAL DESCRIPTION
See block diagram (Fig.1) and definition of levels and
output signals (Chapter “Characteristics” notes 1 to 3;
Figs 3 to 6).
7.1
Signal input stage
(input clamping, blanking and clipping)
The RGB input signals with nominal signal amplitude of
0.7Vb-w are capacitively coupled into the TDA4885 from a
low-ohmic source (75
Ω recommended) and actively
clamped to an internal DC voltage during signal black
level. Because of the high-ohmic input impedance of the
TDA4885 the coupling capacitor (which also functions as
storage capacitor during clamping pulses) can be
relatively small (10 nF recommended). The internal
leakage currents will discharge the coupling capacitor
resulting in black output signals for missing input
clamping pulses.
Composite signals will not disturb normal operations
because a clipping circuit cuts all signal parts below
black level.
A fast signal blanking stage belongs to the input stage
which is driven by several blanking pulses (see Section
“Clamping and blanking pulses”) and control bit DISV = 1.
During the off condition the internal reference black level
will be inserted instead of the input signals.
7.2
Electronic potentiometer stages
7.2.1
CONTRAST CONTROL (DRIVEN BY I2C-BUS,6-BIT
DAC)
The input signals related to the internal reference black
level can be simultaneously adjusted by contrast control
with a control range of typically 32 dB. The nominal
contrast setting is defined for 26H (4 dB below maximum).
7.2.2
BRIGHTNESS CONTROL (DRIVEN BY I2C-BUS,6-BIT
DAC)
With brightness control the video black level will be shifted
in relation to the reference black level simultaneously for
all three channels. With a negative setting (maximum 10%
of nominal signal amplitude) dark signal parts will be lost in
ultra black while for positive settings (maximum 30% of
nominal signal amplitude) the background will alter from
black to grey. The nominal brightness setting (10H) is no
shift. The brightness setting is also valid for OSD signals.
During blanking and output clamping the video black level
will be blanked to reference black level (brightness
blanking).
7.2.3
GAIN CONTROL (DRIVEN BY I2C-BUS,6-BIT DAC)
AND GREY SCALE TRACKING
Gain control is used for white point adjustment (correction
for different voltage to light amplification of the three colour
channels) and therefore individual for the three channels.
The video signals related to the reference black level can
be gain controlled within a range of typical 7 dB.
The nominal setting is maximum gain. The video signal is
the addition of the contrast controlled input signal and the
brightness shift. The gain setting is also valid for OSD
signals, thus the complete ‘grey scale’ is effected by gain
control.
7.3
Output stage
In the output stage the nominal input signal will be
amplified to 2.8Vb-w output colour signal at nominal
contrast and maximum gain. The maximum input-output
amplification at maximum contrast and gain settings is
16 dB. By output clamping the reference black level can
be adjusted. In order to achieve very fast rise and fall times
of the output signals with minimum crosstalk between the
channels, each output stage has its own supply voltage
and ground pin.
7.4
Pedestal blanking
For the video portion the reference black level should
correspond to the ‘extended cut-off voltage’ at the
cathode. During vertical flyback nevertheless retrace lines
may be visible, though blanking to spot cut-off is useful.
With control bit PEDST = 1 the pedestal black level will be
adjusted by output clamping instead of the reference black
level (see Fig.5). The pedestal black level is more negative
than the video black level at minimum brightness setting
and the voltage difference to reference black level is
independent of any user control.
7.5
Output clamping, feedback references and
DAC outputs
Aim of the output clamping (pins FB1, FB2 and FB3) is to
set the reference black level of the signal outputs to a
value which corresponds to the ‘extended cut-off voltage’
of the CRT cathodes. At lack of output clamping pulses the
integrated storage capacitors will discharge resulting in
output signals going to switch-off voltage. Feedback
references are driven by the I2C-bus.




Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56 


Datasheet Download



Related Electronics Part Number

Part NumberComponents DescriptionHtml ViewManufacturer
TDA4886140 MHz video controller with I2C-bus 1 2 3 4 5 MoreNXP Semiconductors
TDA4886A140 MHz video controller with I2C-bus 1 2 3 4 5 MoreNXP Semiconductors
TDA9207150 MHz PIXEL VIDEO CONTROLLER FOR MONITORS INCLUDING CUT-OFF INPUTS 1 2 3 4 5 MoreSTMicroelectronics
TDA9209150 MHz PIXEL VIDEO CONTROLLER FOR MONITORS INCLUDING CUT-OFF INPUTS AND VIDEO DETECTION 1 2 3 4 5 MoreSTMicroelectronics
TDA9210150 MHz PIXEL VIDEO CONTROLLER FOR MONITORS 1 2 3 4 5 MoreSTMicroelectronics
LM1267150 MHz I2C Compatible RGB Video Amplifier System with OSD and DACs 1 2 3 4 5 MoreNational Semiconductor (TI)
STV9211150 MHz PIXEL VIDEO CONTROLLER FOR MONITORS IN DC-COUPLING MODE 1 2 3 4 5 MoreSTMicroelectronics
AD8074500 MHz G = +-1 and +2 Triple Video Buffers with Disable 1 2 3 4 5 MoreAnalog Devices
ADV7129192-Bit 360 MHz True-Color Video DAC with Onboard PLL 1 2 3 4 5 MoreAnalog Devices
MC13283130 MHz VIDEO PROCESSOR WITH OSD INTERFACE 1 2 Motorola, Inc

Link URL

Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Bookmark   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com 2003 - 2017    


Mirror Sites
English : Alldatasheet.com  , Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp  |   Russian : Alldatasheetru.com
Korean : Alldatasheet.co.kr   |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com  |   Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl