TMC22151KHC Fairchild Semiconductor, TMC22151KHC Datasheet - Page 54

• Manufacturer Part Number: TMC22151KHC
• Manufacturer: Fairchild Semiconductor

Specifications of TMC22151KHC

• Screening Level: Commercial
• Package Type: MQFP
• Pin Count: 100
• Lead Free Status / RoHS Status: Compliant

TMC22x5y
Output Processor
Clamp Circuit
A clamp pulse generated by the Burst Gate signal is used to
grab either a sample of the low-pass-filtered luma during the
video back porch, the signal on VIDEOB, or one of two
internally generated levels. The selection is made by the
CLMP[1:0] register bits.
Table 11. Blanking Level Selection
The blanking level is subtracted from the decoded luma.
If the sign is negative, the result is assumed to be mixed sync
and is passed through a delay and into the sync gain stage
within the output matrix. If the sign is positive, the result is
assumed to be pure luma (blanking to peak white) and is fed
to the pedestal removal circuit.
Pedestal Removal
The 8 bit programmable pedestal is subtracted from the pure
luma signal. The negative super black signals are clipped to
zero when register 0Ah bit 4 is set LOW, or the super black
signals are passed through the luma scalar when register 0Ah
bit 4 is HIGH.
54
VIDEOB
U Data
Y Data
V Data
CLMP[1:0]
LPF
00
01
10
11
256
240
CLMP
[1:0]
Clamp
Circuit
–
MSIP
UGx[10:0]
X
VGx[10:0]
External VIDEOB Input
Blanking Selection
Internal LPF Output
X
Internal 240 level
Internal 256 level
PED[7:0]
Mixed Sync
–
Figure 24. Output Processor Block Diagram
ANT
[1:0]
Adaptive Luma
Notch Filter
YSEL ANEN
Fixed (B-Y)
Gain Stage
X
Adaptive Notch Filter
The PAL line-locked comb decoder can never provide
perfect subcarrier cancellation due to the 25Hz offset in the
subcarrier frequency. This 25Hz offset causes residual and
phase modified subcarrier to be left on the luminance signal
which can produce a visible dot crawl on flat areas of color.
However, for all comb filter structures, the quality of the
comb depends on the quality of the sampling clock, as line to
line clock jitter will also cause small phase changes between
the inputs to the comb filter. It is therefore possible that
NTSC comb decoders may also require some coring of the
luma output. To meet the wide range of sample frequencies
that the decoder must deal with two separate coring filters
are selectable.
The luma signal from the pedestal stripper is compared
against the preceding pixel to detect the magnitude change
between pixels. This magnitude difference will be almost
zero for flat areas of picture, and large for high frequency
changes in the picture. The magnitude difference is com-
pared to one of four programmable thresholds. The program-
mable threshold is selected by the ANT
shown in Table 12.
Table 12. Adaptive Notch Threshold Control
SGx[9:0]
YGx[9:0]
ANT
X
X
00
01
10
11
Fixed (R-Y)
Gain Stage
1-0
X
YOFF[8:0]
+
Magnitude difference
+
less than 16
less than 12
less than 8
less than 4
PRODUCT SPECIFICATION
Formatter
Output
1-0
register bits as
G/Y Data
B/Cb Data
R/Cr Data
65-22x5y-65