ADV7183KST Analog Devices Inc, ADV7183KST Datasheet - Page 10

• Manufacturer Part Number: ADV7183KST
• Manufacturer: Analog Devices Inc

Specifications of ADV7183KST

• Adc/dac Resolution: 10b
• Screening Level: Commercial
• Package Type: LQFP
• Pin Count: 80
• Lead Free Status / RoHS Status: Not Compliant

ADV7183
In S-video mode there are two clamp controllers used to sepa-
rately control the luminance clamping and the chrominance
clamping. Also in YCrCb component input mode there are two
clamp controllers used to control the luminance clamping and
the CrCb clamping separately; there are, however, individual
current clamps on the Cr and Cb inputs.
User programmability is built into the clamp controllers which
enable the current and digital clamp controllers to be set up to
user-defined conditions. Refer to analog clamp control register
(14H), digital clamp control register (15H), and digital color
clamp offset register (15H and 16H) for control settings.
ANALOG-TO-DIGITAL CONVERTERS
Two 10-bit ADCs are used in the ADV7183, and they run from
a 27 MHz input clock. An integrated band gap generates the
required reference voltages for the converters. If the decoder is
configured in CVBS mode, the second ADC can be switched off
to reduce power consumption, see PSC[1:0].
AUTOMATIC GAIN CONTROL
The AGC control block on the ADV7183 is a digitally based
system. This controller ensures that the input video signal
(CVBS, S-video, or YCrCb) is scaled to its correct value such
that the YCrCb digital output data matches the correct gain of
the video signal. The AGC has an analog input video range of
0.5 V p-p to 2.0 V p-p, which gives a –6 dB to +6 dB gain range.
Figure 6 demonstrates this range. This AGC range will compensate
for video signals that have been incorrectly terminated or have
been attenuated due to cable loss or other factors.
There are two main control blocks: one for the luminance chan-
nel and one for the chrominance channel.
The luminance automatic gain control has eight modes of
operation:
1. Manual AGC mode where gain for the luminance path is set
2. Blank level to sync tip is used to set the luminance gain;
3. Blank level to sync tip is used to set luminance gain; manual
4. Blank level to sync tip is used to set luminance gain;
manually using LGM[11:0].
manual MIRE[2:0] controls the maximum value through the
luminance channel. There is no override of this mode when
white peak mode is detected.
MIRE[2:0] controls the maximum value through luminance
channel. There is override of this mode when white peak
mode is detected. White peak mode is activated when the
input video exceeds the maximum luminance range for long
periods; this mode is designed to prevent clipping of the
input video signal.
MIRE[2:0] is automatically controlled to set the maximum
value through the luminance channel. There is no override
of this mode when white peak mode is detected.
5. Blank level to sync tip is used to set luminance gain; manual
6. Based on active video peak white. PW_UPD sets the gain
7. Based on average active video. PW_RES sets what lines are used;
8. The luminance channel gain is frozen at its present value.
The chrominance automatic gain control has four modes of
operation:
1. Manual AGC mode where gain for chrominance path is set
2. Luminance gain used for chrominance channel.
3. Chrominance automatic gain based on color burst amplitude.
4. Chrominance gain frozen at its present setting.
Both the luminance and chrominance AGC controllers have a
programmable time constant that allows the AGC to operate in
four modes: slow, medium, fast, and video quality controlled.
The maximum IRE (MIRE[2:0]) control can be used to set the
maximum input video range that can be decoded. Table I shows
the selectable range.
MIRE[2:0]
0
0
0
0
1
1
1
1
MIRE[2:0] is automatically controlled to set the maximum
value through the luminance channel. There is override of
this mode when white peak mode is detected. White peak
mode is activated when the input video exceeds the maxi-
mum luminance range for long periods; this mode is designed
to prevent clipping of the input video signal.
update frequency (once per field).
only relevant if the signal conforms to PAL 625 line standard.
manually using CGM[11:0].
0
0
1
1
0
0
1
1
–6
6
0
0
1
0
1
0
1
0
1
MAXIMUM
MINIMUM
RANGE = 12dB
Table I. MIRE Control
PAL (IRE)
133
125
120
115
110
105
100
100
Function
122
115
110
105
100
100
100
100
NTSC (IRE)
0