參數(shù)資料
型號(hào)： TDA9330
廠商： NXP Semiconductors N.V.
英文描述： I2C-bus controlled TV display processors
中文描述： 的I2C控制的電視顯示處理器總線
文件頁數(shù)： 7/56頁
文件大?。?/td> 228K
代理商： TDA9330
2000 May 08
7
Philips Semiconductors
Preliminary specification
I
2
C-bus controlled TV display processors
TDA933xH series
FUNCTIONAL DESCRIPTION
RGB control circuit
I
NPUT SIGNALS
The RGB control circuit of the TDA933xH contains three
sets of input signals:
YUV input signals, which are supplied by the input
processor or the feature box. Bit GAI can be used to
switch the luminance input signal sensitivity between
0.45 V (p-p) and 1.0 V (b-w). The nominal input signals
for U and V are 1.33 V (p-p) and 1.05 V (p-p),
respectively. These input signals are controlled on
contrast, saturation and brightness.
The first RGB input is intended for external signals
(SCART in 1f
H
and VGA in 2f
H
applications), which have
an amplitude of 0.7 V (p-p) typical. This input is also
controlled on contrast, saturation and brightness.
The second RGB input is intended for OSD and teletext
signals. The required input signals have an amplitude of
0.7 V (p-p). The switching between the internal signal
and the OSD signal can be realized via a blending
function or via fast blanking. This input is only controlled
on brightness.
Switching between the various sources can be realized via
the I
2
C-bus and by fast insertion switches. The fast
insertion switches can be enabled via the I
2
C-bus.
The circuit contains switchable matrix circuits for the
colour difference signals so that the colour reproduction
can be adapted for PAL/SECAM and NTSC. For NTSC,
two different matrices can be chosen. In addition, a matrix
for high-definition ATSC signals is available.
O
UTPUT AMPLIFIER
The output signal has an amplitude of approximately
2 V (b-w) at nominal input signals and nominal settings of
the controls. The required ‘white point setting’ of the
picture tube can be realized by means of three separate
gain settings for the RGB channels.
To obtain an accurate biasing of the picture tube, a CCC
circuit has been developed. This function is realized by a
2-point black level stabilization circuit.
Byinsertingtwotestlevelsforeachgunandcomparingthe
resulting cathode currents with two different reference
currents, the influence of the picture tube parameters such
as the spread in cut-off voltage can be eliminated.
This 2-point stabilization is based on the principle that the
ratio between the cathode currents is coupled to the ratio
between the drive voltages according to:
The feedback loop makes the ratio between cathode
currents I
k1
and I
k2
equal to the ratio between the
reference currents (which are internally fixed) by changing
the (black) level and the amplitude of the RGB output
signals via two converging loops. The system operates in
such a way that the black level of the drive signal is
controlled to the cut-off point of the gun. In this way, a very
good grey scale tracking is obtained. The accuracy of the
adjustment of the black level is only dependent on the ratio
ofinternal currentsand thesecanbemadevery accurately
in integrated circuits. An additional advantage of the
2-point measurement is that the control system makes the
absolute value of I
k1
and I
k2
identical to the internal
reference currents. Because this adjustment is obtained
by adapting the gain of the RGB control stage, this control
stabilizes the gain of the complete channel (RGB output
stage and cathode characteristic). As a result, this 2-point
loop compensates for variations in the gain figures during
life.
An important property of the 2-point stabilization is that the
offset and the gain of the RGB path are adjusted by the
feedback loop. Hence, the maximum drive voltage for the
cathode is fixed by the relationship between the test
pulses, the reference current and the relative gain setting
of the three channels. Consequently, the drive level of the
CRT cannot be adjusted by adapting the gain of the RGB
output stage. Because different picture tubes may require
different drive levels, the typical ‘cathode drive level’
amplitude can be adjusted by means of an I
2
C-bus setting.
Depending on the selected cathode drive level, the typical
gain of the RGB output stages can be fixed, taking into
account the drive capability of the RGB outputs
(pins 40 to 42). More details about the design are given in
the application report (see also Chapter “Characteristics”;
note 11).
The measurement of the high and the low currents of the
2-point stabilization circuit is performed in two consecutive
fields. The leakage current is measured in each field. The
maximum allowable leakage current is 100
μ
A.
For extra flexibility, it also possible to switch the CCC
circuit to 1-point stabilization with the OPC bit. In this
mode, only the black level at the RGB outputs is controlled
by the loop. The cathode drive level setting has no
influence on the gain in this mode. This level should be set
to the nominal value to get the correct amplitude of the
measuring pulses.
I
k2
I
V
V
dr1
----------
γ
=
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