ADV7189B View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADV7189B' PDF : 104 Pages View PDF
ADV7189B
CSFM[2:0] C-Shaping Filter Mode, Address 0x17[7]
The C-shaping filter mode bits allow the user to select from a
range of low-pass filters, SH1 to SH5, and wideband mode for
the chrominance signal. The auto-selection options
automatically select from the filter options to give the specified
response. (See settings 000 and 001 in Table 182H 32).
Table 32. CSFM Function
CSFM[2:0]
Description
000 (default) Autoselect 1.5 MHz bandwidth
001
Autoselect 2.17 MHz bandwidth
010
SH1
011
SH2
100
SH3
101
SH4
110
SH5
111
Wideband mode
COMBINED C ANTIALIAS, C SHAPING FILTER,
C RESAMPLER
0
–10
–20
–30
–40
–50
–60
0
1
2
3
4
5
6
FREQUENCY (MHz)
Figure 16. Chroma Shaping Filter Responses
Figure 183H 16 shows the responses of SH1 (narrowest) to SH5
(widest) in addition to the wideband mode.
GAIN OPERATION
The gain control within the ADV7189B is done on a purely
digital basis. The input ADCs support a 12-bit range, mapped
into a 1.6 V analog voltage range. Gain correction takes place
after the digitization in the form of a digital multiplier.
Advantages of this architecture over the commonly used
programmable gain amplifier (PGA) before the ADCs include
the fact that the gain is now completely independent of supply,
temperature, and process variations.
As shown in Figure 184H 17, the ADV7189B can decode a video signal
as long as it fits into the ADC window. The two components to
this are the amplitude of the input signal and the dc level it resides
on. The dc level is set by the clamping circuitry (see the Clamp 185H
Operation section).
If the amplitude of the analog video signal is too high, clipping
can occur, resulting in visual artifacts. The analog input range
of the ADC, together with the clamp level, determines the
maximum supported amplitude of the video signal.
The minimum supported amplitude of the input video is
determined by the ADV7189B’s ability to retrieve horizontal
and vertical timing and to lock to the colorburst, if present.
There are separate gain control units for luma and chroma data.
Both can operate independently of each other. The chroma unit,
however, can also take its gain value from the luma path.
The possible AGC modes are summarized in Table 186H 33.
It is possible to freeze the automatic gain control loops. This
causes the loops to stop updating, and the AGC determined
gain at the time of the freeze to stay active until the loop is
either unfrozen or the gain mode of operation is changed.
The currently active gain from any of the modes can be read
back. Refer to the description of the dual-function manual gain
registers, LG[11:0] Luma Gain and CG[11:0] Chroma Gain, in
the Luma 187H Gain and the 18HChroma Gain sections.
MAXIMUM
VOLTAGE
ANALOG VOLTAGE
RANGE SUPPORTED BY ADC (1.6V RANGE FOR ADV7189B)
MINIMUM
VOLTAGE
CLAMP
LEVEL
ADC
DATA
PRE-
PROCESSOR
(DPP)
SDP
(GAIN SELECTION ONLY)
GAIN
CONTROL
Figure 17. Gain Control Overview
Rev. B | Page 30 of 104
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