ADV7283 Data Sheet
Rev. A | Page 10 of 21
THEORY OF OPERATION
The ADV7283 is a versatile one-chip, multiformat video
decoder. The device automatically detects standard analog
baseband video signals compatible with worldwide NTSC, PAL,
and SECAM standards in the form of composite, S-Video, and
component video.
The ADV7283 converts the analog video signals into an 8-bit
YCrCb 4:2:2 video data stream that is compatible with the 8-bit
ITU-R BT.656 interface standard.
The analog video inputs of the ADV7283 accept single-ended,
pseudo differential, and fully differential composite video signals,
as well as S-Video and YPrPb video signals, supporting a wide
range of consumer and automotive video sources.
In differential CVBS mode, the ADV7283, along with an
external resistor divider, provides a common-mode input range
of up to 4 V, enabling the removal of large signal, common-mode
transients present on the video lines.
The advanced I2P function allows the ADV7283 to convert an
interlaced video input into a progressive video output. This
function is performed without the need for external memory.
The ADV7283 uses edge adaptive technology to minimize
video defects on low angle lines.
The AGC and clamp restore circuitry allow an input video
signal peak-to-peak range of 1.0 V p-p at the analog video input
pins of the ADV7283. Alternatively, the AGC and clamp restore
circuitry can be bypassed for manual settings.
The external ac coupling capacitors protect the ADV7283 from
short-to-battery (STB) events on the analog video input pins.
The ADV7283 supports a number of other functions, including
8-bit to 6-bit down dither mode and ACE.
The ADV7283 is programmed via a 2-wire, serial bidirectional
port (I
2
C compatible) and is fabricated in a 1.8 V CMOS
process. The monolithic CMOS construction of the ADV7283
ensures greater functionality with lower power dissipation.
The ADV7283 is provided in a space-saving LFCSP surface-
mount, RoHS-compliant package.
The ADV7283 is available in an automotive grade that is rated
over the−40°C to +105°C temperature range, making the device
ideal for automotive applications.
The ADV7283 is also available in a −40°C to +85°C temperature
range, making it ideal for industrial applications.
ANALOG FRONT END
The analog front end (AFE) of the ADV7283 comprises a single
high speed, 10-bit ADC that digitizes the analog video signal
before applying it to the standard definition processor (SDP).
The AFE uses differential channels to the ADC to ensure high
performance in mixed-signal applications and to enable different ial
CVBS inputs to connect directly to the ADV7283.
The AFE also includes an input mux that enables the
application of multiple video signals to the ADV7283. The input
mux allows the application of up to six composite video signals to
the ADV7283.
Current clamps are positioned in front of the ADC to ensure
that the video signal remains within the range of the converter.
A resistor divider network is required before each analog input
channel to ensure that the input signal is kept within the range
of the ADC (see the Input Networks section). Fine clamping of
the video signal is performed downstream by digital fine
clamping within the ADV7283.
Table 9 lists the three ADC clock rates that are determined by
the video input format to be processed. These clock rates ensure
4× oversampling per channel for CVBS, Y/C, and YPrPb modes.
Table 9. ADC Clock Rates
Input Format
ADC Clock Rate
(MHz)
1
Oversampling
Rate per
Channel
CVBS (Composite) 57.27 4×
Y/C (S-Video) 114 4×
YPrPb (Component) 172 4×
1
Based on a 28.63636 MHz crystal between the XTALP and XTALN pins.
The fully differential AFE of the ADV7283 provides inherent
small and large signal noise rejection, improved
electromagnetic interference (EMI) protection, and the ability
to absorb ground bounce. Support is provided for both true
differential and pseudo differential signals.
