ADV7181BCP Analog Devices Inc, ADV7181BCP Datasheet - Page 31

• Manufacturer Part Number: ADV7181BCP
• Description: IC VIDEO DECODER NTSC 64-LFCSP
• Manufacturer: Analog Devices Inc
• Type: Video Decoderr

Specifications of ADV7181BCP

• Applications: Recorders, Set-Top Boxes
• Voltage - Supply, Analog: 3.15 V ~ 3.45 V
• Voltage - Supply, Digital: 1.65 V ~ 2 V
• Mounting Type: Surface Mount
• Package / Case: 64-LFCSP
• Adc/dac Resolution: 9b
• Screening Level: Industrial
• Package Type: LFCSP EP
• Pin Count: 64
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With: EVAL-ADV7181BEB - BOARD EVALUATION FOR ADV7181
• Lead Free Status / RoHS Status: Compliant, Contains lead / RoHS non-compliant

GAIN OPERATION
The gain control within the ADV7181 is done on a purely
digital basis. The input ADCs support a 9-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 is the fact that the gain is now completely
independent of supply, temperature, and process variations.
As shown in Figure 16, the ADV7181 can decode a video signal
as long as it fits into the ADC window. There are two components
Table 62. AGC Modes
Input Video Type
Any
CVBS
Y/C
YPrPb
–10
–20
–30
–40
–50
–60
0
0
Figure 15. Chroma Shaping Filter Responses
1
COMBINED C ANTIALIAS, C SHAPING FILTER,
2
MINIMUM
VOLTAGE
FREQUENCY (MHz)
C RESAMPLER
Luma Gain
Manual gain luma.
Dependent on horizontal sync depth.
Peak White
Dependent on horizontal sync depth.
Peak White.
Dependent on horizontal sync depth.
MAXIMUM
VOLTAGE
3
4
CLAMP
LEVEL
5
6
Figure 16. Gain Control Overview
Rev. B | Page 31 of 104
ANALOG VOLTAGE
RANGE SUPPORTED BY ADC (1.6V RANGE FOR ADV7181)
ADC
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.
The minimum supported amplitude of the input video is
determined by the ADV7181’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 62 summarizes them.
It is possible to freeze the automatic gain control loops. This
causes the loops to stop updating. 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.
PROCESSOR
DATA
(DPP)
PRE
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.
SDP
(GAIN SELECTION ONLY)
CONTROL
GAIN
ADV7181