PRODUCT SPECIFICATION
TMC22091/TMC22191
PXCK
0
1
2
3
4
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76
GHSYNC
CVBS
7-0
f23:20 f19:16 f15:12 f11:8 f7:4 f3:0 φ23:20 φ19:16 φ15:12 φ11:8 φ7:4 φ3:0
PIXEL
PIXEL
PIXEL FID
PIXEL
PIXEL
FREQUENCY
PHASE
24383A
FIELD IDENTIFICATION
Figure 25. Frequency/Phase Data Transfer
Since these are fixed-coefficient digital filters, their filter
characteristics depend upon clock rate. Figures 26 and 27
show the frequency response for two pixel rates, 12.27 MHz
and 14.75 MHz.
Filtering
The TMC22x91 incorporates internal digital filters to estab-
lish appropriate bandwidths and simplify external analog fil-
ter designs.
0
Color-Difference Low-Pass Filters
-10
f = 14.75 Mpps
The color-difference low-pass filters in the TMC22x91
establish chrominance bandwidths which meet the specifica-
tions outlined in CCIR Report 624-3, Table II, Item 2.6, for
system I over a range of pixel rates from 12.27 Mpps to
14.75 Mpps. Equal bandwidth is established for both color-
difference channels.
-20
-30
-40
f = 12.27 Mpps
-50
-60
-70
-80
-90
0
0
3
6
9
12
15
CCIR Rep 624 Specification
-10
Frequency (MHz)
24394A
-20
Figure 27. Chroma Modulator and Luminance
Interpolation Filter Full Spectrum Response
f = 14.27 Mpps
-30
-40
-50
-60
-70
-80
-90
f = 12.27 Mpps
f = 14.75 Mpps
0
-1
-2
-3
-4
0
1
2
3
4
5
6
7
8
f = 12.27 Mpps
Frequency (MHz)
24363A
Figure 26. Color-Difference Low-Pass Filter Response
Interpolation Filters
0
1
2
3
4
5
6
7
Frequency (MHz)
24365A
The Chroma Modulator output and the luminance data path
are digitally filtered with sharp-cutoff low-pass interpolation
filters. These filters ensure that aliased subcarrier, chromi-
nance, and luminance frequencies are sufficiently suppressed
in the frequency band above base-band video and below the
Figure 28. Chroma Modulator and Luminance
Interpolation Filter Passband Detail
All digital-to-analog reconstruction systems exhibit a high
frequency roll-off as a result of the zero-order hold charac-
teristic of D/A converters. This response is commonly
referred to as a sin(x)/x response. It is a function of the sam-
pling rate of the output D/A.
pixel frequency (f /4 to 3f /4, where f is the PXCK
S
S
S
frequency).
45
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