EVAL-ADV7183BEB View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'EVAL-ADV7183BEB' PDF : 104 Pages View PDF
ADV7183A
COMBINED C ANTIALIAS, C SHAPING FILTER,
C RESAMPLER
0
–10
–20
–30
–40
As shown in Figure 17, the ADV7183A can decode a video
signal as long as it fits into the ADC window. There are two
components to this: 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 Operation section).
If the amplitude of the analog video signal is too high, clipping
may 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.
–50
–60
0
1
2
3
4
5
6
FREQUENCY (MHz)
Figure 16. Chroma Shaping Filter Responses
GAIN OPERATION
The gain control within the ADV7183A is done on a purely
digital basis. The input ADCs support a 10-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.
There are several advantages of this architecture over the
commonly used PGA (programmable gain amplifier) before the
ADCs; among them the gain is now completely independent of
supply, temperature, and process variations.
The minimum supported amplitude of the input video is
determined by the ADV7183A’s ability to retrieve horizontal
and vertical timing and to lock to the color burst, if present.
There are two gain control units, one each 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.
Several AGC modes are possible; Table 63 summarizes them.
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 stays 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 Gain and Chroma Gain sections.
MAXIMUM
VOLTAGE
ANALOG VOLTAGE
RANGE SUPPORTED BY ADC (1.6V RANGE FOR ADV7183A)
MINIMUM
VOLTAGE
CLAMP
LEVEL
ADC
DATA
PRE
PROCESSOR
(DPP)
SDP
(GAIN SELECTION ONLY)
GAIN
CONTROL
Table 63. AGC Modes
Input Video Type
Any
CVBS
Y/C
YPrPb
Figure 17. Gain Control Overview
Luma Gain
Manual gain luma.
Dependent on horizontal sync depth.
Peak White
Dependent on horizontal sync depth.
Peak White.
Dependent on horizontal sync depth.
Chroma Gain
Manual gain chroma.
Dependent on color burst amplitude.
Taken from luma path.
Dependent on color burst amplitude.
Taken from luma path.
Dependent on color burst amplitude.
Taken from luma path.
Dependent on color burst amplitude.
Taken from luma path.
Taken from luma path.
Rev. B | Page 32 of 104
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