TMC22191 CADEKA [Cadeka Microcircuits LLC.], TMC22191 Datasheet - Page 45

• Manufacturer Part Number: TMC22191
• Description: Digital Video Encoders/Layering Engine
• Manufacturer: CADEKA [Cadeka Microcircuits LLC.]

PRODUCT SPECIFICATION
Filtering
The TMC22x91 incorporates internal digital filters to estab-
lish appropriate bandwidths and simplify external analog fil-
ter designs.
Color-Difference Low-Pass Filters
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.
Interpolation Filters
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
pixel frequency (f
frequency).
GHSYNC
Figure 26. Color-Difference Low-Pass Filter Response
CVBS 7-0
-10
-20
-30
-40
-50
-60
-70
-80
-90
PXCK
0
0
0
1
PIXEL
1
S
/4 to 3f
2
2
f = 12.27 Mpps
PIXEL
3
3
Frequency (MHz)
S
/4, where f
4
4
57
CCIR Rep 624 Specification
FIELD IDENTIFICATION
PIXEL
S
58
5
is the PXCK
Figure 25. Frequency/Phase Data Transfer
59
FID f
6
f = 14.27 Mpps
60
23:20
61
7
f
19:16
24363A
62
FREQUENCY
f
15:12
8
63
f
11:8
64
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.
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.
f
7:4
-10
-20
-30
-40
-50
-60
-70
-80
-90
65
-1
-2
-3
-4
0
0
Figure 27. Chroma Modulator and Luminance
Figure 28. Chroma Modulator and Luminance
0
f
Interpolation Filter Full Spectrum Response
3:0
0
66
23:20 19:16 15:12 11:8
Interpolation Filter Passband Detail
67
1
3
68
f = 12.27 Mpps
PHASE
2
69
f = 12.27 Mpps
Frequency (MHz)
Frequency (MHz)
70
3
6
7:4
71
3:0
4
72
9
73
TMC22091/TMC22191
5
f = 14.75 Mpps
PIXEL
74
f = 14.75 Mpps
12
6
75
PIXEL
24383A
76
24394A
24365A
7
15
45