TDA9550 PHILIPS [NXP Semiconductors], TDA9550 Datasheet - Page 101

• Manufacturer Part Number: TDA9550
• Description: TV signal processor-Teletext decoder with embedded m-Controller
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
32. The contrast and saturation control is active on the internal signal (YUV) and on the external RGB/YUV input. The
33. The YUV/YP
34. When the decoder is forced to a fixed subcarrier frequency (via the CM-bits) the chroma trap is always switched-on,
35. Valid for a signal amplitude on the Y-input of 0.7 V black-to-white (100 IRE) with a rise time (10% to 90%) of 70 ns
36. The ratio between the positive and negative peaks can be varied by means of the bits RPO1 and RPO0 in
37. The coring can be activated in the low-light part of the picture. This effectively reduces the noise while having
38. For video signals with a black level which deviates from the back-porch blanking level the signal is “stretched” to the
39. The Dynamic Skin Tone Correction circuit is designed such that it corrects (instantaneously and locally) the hue of
40. Stretching is 50% when the average video content has the level which is chosen with these bits. The stretching varies
41. Via the ‘blue stretch’ (BLS bit) function the colour temperature of the bright scenes (amplitudes which exceed a value
42. The slicing level is independent of sync pulse amplitude. The given percentage is the distance between the slicing
43. To obtain a good performance for both weak signal and VCR playback the time constant of the first control loop is
2000 Jun 22
TV signal processor-Teletext decoder with
embedded -Controller
Text/OSD input can be controlled on brightness only. Nominal contrast is specified with the DAC in position 20 HEX.
Nominal saturation as maximum 10 dB.
also when no colour signal is identified. In the automatic mode the chroma trap is switched-off when no colour signal
is identified.
and the video switch in the Y/C mode. During production the peaking function is not tested by measuring the
overshoots but by measuring the frequency response of the Y output.
subaddress 2EH. For ratios which are smaller than 1.8 the positive peak is not affected and the negative peak is
reduced.
maximum peaking in the bright parts of the picture. The setting the video content at which the coring is active can be
adapted by means of the COR1/COR0 bits in subaddress 2DH.
blanking level. The amount of correction depends on the IRE value of the signal (see Fig.40). The black level is
detected by means of an internal capacitor. The black level stretcher can be switched on and off via the BKS bit in
subaddress 2DH. The values given in the specification are valid only when the luminance input signal has an
amplitude of 1 V
those colours which are located in the area in the UV plane that matches to skin tones. The correction is dependent
on the luminance, saturation and distance to the preferred axis. Because the amount of correction is dependent on
the parameters of the incoming YUV signal it is not possible to give exact figures for the correction angle. The
correction angle of 45 ( 22.5) degrees is just given as an indication and is valid for an input signal with a luminance
signal amplitude of 75% and a colour saturation of 50%. A graphical representation of the control behaviour is given
in Figure 41 on page 112.
from 100% to 0% over an average video range of 25% to 30%.
of 80% of the nominal amplitude) can be increased. This effect is obtained by decreasing the small signal gain of the
red and green channel signals which exceed the 80% level. The effect is illustrated in Figure 42 on page 113.
level and the black level (back porch). When the amplitude of the sync pulse exceeds the value of 350 mV the sync
separator will slice the sync pulse at a level of 175 mV above top sync. The maximum sync pulse amplitude is 4 V
The vertical slicing level is dependent on the S/N ratio of the incoming video signal. For a S/N
level is 35%, for a S/N
level can be forced to 60%.
switched depending on the input signal condition and the condition of the POC, FOA, FOB and VID bits in
subaddress 24H. The circuit contains a noise detector and the time constant is switched to ‘slow’ when too much
noise is present in the signal. In the ‘fast’ mode during the vertical retrace time the phase detector current is increased
50% so that phase errors due to head-switching of the VCR are corrected as soon as possible. Switching of the time
constant can be automatically or can be set by means of the control bits.
The circuit contains a video identification circuit which is independent of the first loop. This identification circuit can
be used to close or open the first control loop when a video signal is present or not present on the input. This enables
a stable On Screen Display (OSD) when just noise is present at the input.
B
P
R
p-p
input signal amplitudes are based on a colour bar signal with 75/100% saturation.
.
24 dB the slicing level is 60%. With the bit FSL (Forced Slicing Level) the vertical slicing
101
TDA955X/6X/8X PS/N1 series
Tentative Device Specification
24 dB the slicing
p-p
.