MC13077 Datasheet, PDF (8/14 Pages) Motorola, Inc – ADVANCED PAL/NTSC ENCODER

MC13077
Figure 5. Relationship Showing the Counts of a 3.58 MHz Clock
versus a 4.43 MHz Clock at the End of a Horizontal Period
fsc
fsc/256
256
512
NTSC: (3.58 MHz) (63.56 µs) = 227.5 counts
PAL: (4.43 MHz) (64 µs) = 283.75 counts
Chroma Band Limiting and Luma Delay
Once the color difference and burst flag envelopes have
been modulated, the two components are internally summed
and applied to an output buffer that will drive the external
bandpass circuitry before entering the chip again at Pin 20.
The sum of the color difference modulators produces an
output that is high in harmonic content. For this reason, and
to reduce the possibility of cross color, a chroma bandpass
transformer is used to band–limit the chroma. Suggested
bandpass filters and specifications for NTSC and PAL are
shown in Figure 6a and 6b. For each of these filters,
approximately 300 ns of group delay is experienced by the
filtered chroma. There is also an internal delay on the order of
100 ns due to internal filtering that must be considered. Thus
a 400 ns luma delay line is used to equalize the timing of the
luma and the chroma. Suitable 400 ns delay lines are the
TOKO H321LNP–1436PBAB and the TDK
DL122401D–1533. The delay of the luma channel is inserted
between Pins 10 and 6. Pin 10 is the buffered output of the
luma from the RGB matrix. This output is capable of driving
the external passive delay line with no external gain or
buffering required.
Figure 6a. Group Delay and Magnitude
Response of the TOKO Bandpass Filter
Intended for NTSC Applications
0
10 ^Attenuation
TOKO H286BAlS–6276DAD
20
NTSC Bandpass Filter
1.0 k
4.7 nF
30
17
13
20
64
1.0 k
40
0.4
50
0.2
Group Delay
60
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
FREQUENCY (MHz)
Figure 6b. Group Delay and Magnitude
Response of the TOKO Bandpass Filter
Intended for PAL Applications
0
10
Attenuation
TOKO H286BAIS–4963DAD
20
PAL Bandpass Filter
1.0 k
4.7 nF
30
17
13
20
64
1.0 k
40
0.4
50
0.2
Group Delay
60
0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0
FREQUENCY (MHz)
Characteristics of TOKO Bandpass Filter
(H286BAIS – 6276DAD)
Frequency (MHz) Attenuation (dB) Group Delay (µs)
2.0
8.0 (min)
0.12
2.8
3.0 ± 3.0
0.25
3.58
Ins. Loss 3.5 (max)
0.290 ± 0.030
4.3
3.0 ± 3.0
0.24
6.2
15 (min)
0.05
Characteristics of TOKO Bandpass Filter
(H286BAIS – 4963DAD)
Frequency (MHz) Attenuation (dB) Group Delay (µs)
2.50
10 (min)
0.075
3.73
3.0 ± 3.0
0.24
4.43
Ins Loss 2.0 (max)
0.295 ± 0.035
5.13
3.0 ± 3.0
0.24
6.50
12 (min)
0.05
8
MOTOROLA ANALOG IC DEVICE DATA