ml6440 Micro Electronics Corporation, ml6440 Datasheet - Page 15

• Manufacturer Part Number: ml6440
• Description: Multi-standard 8-bit Adaptive Digital Input Comb Filter
• Manufacturer: Micro Electronics Corporation

PERFORMANCE DATA
COMB FILTER PERFORMANCE
• Unrestricted Bandwidth. No band-limiting is performed
• High frequency peaking allows for gentle transitions
• Spurious sub-carrier supression by 48dB removes color
NOTCH FILTER PERFORMANCE
• When invoked by adaption threshold logic, hanging dot
ADAPTIVE THRESHOLD PERFORMANCE
• Seven fixed values to select threshold, the 8th value is
• Adaptive thresholds improve around 10% per threshold
• D[6:4] = 000 is the automatic self-adjusting threshold
on the signal when the comb is on hence preventing a
signal loss.
from comb to notch modes.
sub-carrier which otherwise can cause large area dot
crawl
suppression is 35dB.
for automatic self-adjusting threshold mode.
level. However, adaptive thresholds can surpass
optimum threshold thus causing smearing effects.
mode. D[6:4] = 001 is the low threshold and D[6:4] =
111 is the highest threshold, D[6:4] = 010 to 110 is
therefore the intermediate thresholds.
Figure 11. NTSC Luma Notch Filter CCIR
–0.5
1.5
1.0
0.5
0
0
1
FREQUENCY (MHz)
2
3
4
5
6
Figures 11 through 20 show the bandwidth of notch,
chroma bandpass, and comb filters for NTSC and PAL
video. These curves were taken from a VM700 using a
sweep frequency pattern using a TG2000 on the
ML6440EVAL board.
Figure 11 shows the NTSC luma filter at CCIR clock rates.
This shows significant notch from 3.3MHz to 4MHz
sufficient for hanging dot suppression. Figure 12 shows
the NTSC chroma bandpass filter for CCIR clock rates
where the filter at 3dB ranges from 3MHz to 4.5Mhz.
Figure 13 shows the luma notch filter for NTSC for
hanging dot suppression for Square Pixel clock rates. This
notch ranges from 3.3MHz to 4MHz. Figure 14 shows the
NTSC chroma bandpass filter running at Square Pixel
clock rates where it at 3dB ranges from 3MHz to 4.5MHz.
Figure 15 shows PAL luma response for hanging dot
suppression at Square Pixel clock rates where notch
ranges from 3.3MHz to 4MHz. Figure 16 shows the
response of the PAL chroma bandpass filter where at 3dB
down ranges from 3MHz to 4.2MHz. Figure 17 shows the
PAL notch filter for luma hanging dot suppression at CCIR
clock rates where the notch ranges from 4MHz to 4.3MHz
at zero amplitude. Figure 18 shows the bandpass filter for
PAL at the CCIR clock rate where at 3dB down ranges
from 3.3MHz to 4.7MHz. Figure 19 shows the NTSC
luma comb response over a line-to-line in phase
frequency sweep to 6MHz for CCIR clock rates. Figure 20
shows the NTSC luma response over a line-to-line in
phase frequency sweep to 6MHz for Square Pixel clock
rate.
Figure 12. NTSC Chroma Band Phase Filter, CCIR
–0.5
1.5
1.0
0.5
0
0
1
FREQUENCY (MHz)
2
3
4
ML6440
5
6
15