tda4680wp NXP Semiconductors, tda4680wp Datasheet - Page 18

• Manufacturer Part Number: tda4680wp
• Description: Video Processor With Automatic Cut-off And White Level Control
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9. The vertical blanking interval is defined by a vertical pulse which contains 4 (8) or more horizontal pulses; it begins
10. During picture cathode warming up (first switch-on delay) the RGB outputs (pins 24, 22 and 20) are blanked to the
11. Range of cut-off measurement level at the RGB outputs is 1 to 5 V. The recommended value is 3 V.
12. The hue control output at pin 26 is an emitter follower with current source.
Table 5 Demodulator axes and amplification factors
Table 6 PAL/SECAM and NTSC matrix; notes 1 and 2
Notes
1. PAL/SECAM signals are matrixed by the equation: V
2. The vertical blanking interval is selected via the I
1996 Oct 25
(B
(R
(R
(B
Video processor with automatic cut-off and
white level control
with the start of the vertical pulse and ends with the end of the white measuring line. If the vertical pulse is longer
than the selected vertical blanking window the blanking period ends with the end of the complete line after the end
of the vertical pulse. The counter cycle time is 31 (63) horizontal pulses. If the vertical pulse contains more than
29 (57) horizontal pulses, the black level storage capacitors will be discharged while all signals are blanked.
During leakage current measurement, the RGB channels are blanked to ultra-black level. During cut-off
measurement one channel is set to the measurement pulse level, the other channels are blanked to ultra-black.
Since the brightness adjust shifts the colour signal relative to the black level, the brightness adjust is disabled during
the vertical blanking interval (see Figs 7 and 8).
ultra-black level during line scan. During the vertical blanking interval a white-level monitor pulse is fed out on the
RGB outputs and the cathode currents are measured. When the voltage threshold on pin 19 is greater than 5.0 V,
the monitor pulse is switched off and cut-off and white level control are activated (second switch-on delay). As soon
as cut-off control stabilizes, RGB output blanking is removed.
NTSC signals are matrixed by the equations (hue phase shift of 5 degrees):
V
In the matrix equations: V
the NTSC demodulator. V
to the demodulator axes and amplification factors shown in Table 5. V
the vertical component of the sandcastle pulse; this vertical component has priority when it is longer than the vertical
blanking interval of the transmission standard.
R
Y)* demodulator axis
Y)* demodulator axis
Y)* amplification factor
Y)* amplification factor
Y*
= 1.57V
R Y
PARAMETER
PAL/SECAM
MATRIX
0.41V
NTSC
G
R
B Y
Y*
Y
, V
and V
; V
R
G
Y*
B
Y*
and V
Y
= 0.43V
are conventional PAL demodulation axes and amplitudes at the output of
B
Y*
2
R Y
are the NTSC-modified colour difference signals; this is equivalent
C-bus (see Table 2 and Fig.8). Vertical blanking is determined by
G
18
0.11V
Y
= 0.51V
B
Y
; V
R Y
NTSC
115
1.97
2.03
B
0
G
Y*
Y*
0.19V
= V
= 0.27V
B
B
Y
NMEN
Y
0
1
R
Y*
0.22V
Product specification
B
PAL
1.14
2.03
TDA4680
90
0
Y*
.