ADV7182ABCPZ datasheet(11/102 Pages) AD

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Data Sheet

ADV7182A

Rev. 0 | Page 11 of 102

THEORY OF OPERATION

The ADV7182A is a versatile, multiformat video decoder that

automatically detects standard analog baseband video signals

and converts them into a YCbCr 4:2:2 component video data

stream. The ADV7182A supports video signals compatible with

worldwide NTSC, PAL, and SECAM standards.

The analog front end (AFE) of the ADV7182A features a 4-channel

input mux, a differential to single-ended converter, and a single

10-bit ADC. The analog video inputs accept single-ended, pseudo

differential, and fully differential composite video signals, as well as

S-Video and YPbPr video signals, supporting a wide range of

consumer and automotive video sources, making the ADV7182A

ideal for automotive, industrial, and consumer applications.

The ADV7182A converts these analog video formats into a

digital 8-bit ITU-R BT.656 video stream. External HS, VS, and

FIELD signals provide timing references for liquid crystal display

(LCD) controllers and other video application specific

integrated circuits (ASICs).

The digital video output stream of the ADV7182A interfaces

easily to a wide range of mobile video processors, MPEG

encoders, codecs, and Analog Devices digital video encoders,

such as the ADV7391.

The ADV7182A is programmed via a 2-wire, serial bidirectional

port (I2C compatible) and can communicate with other devices

using the hardware interrupt pin.

The ADV7182A is fabricated in a low power, 1.8 V CMOS

process. The device is provided in a space-saving, LFCSP,

surface-mount, RoHS compliant package. The ADV7182A is

available in an automotive grade rated over the −40°C to +105°C

temperature range, making the ADV7182A ideal for automotive

applications. The ADV7182A is also available in a −40°C to

+85°C temperature range, making it ideal for consumer or

industrial applications.

ANALOG FRONT END (AFE)

The ADV7182A AFE is comprised of a 4-channel input mux, a

differential to single-ended converter with clamp circuitry, a set

of four antialiasing filters, and a single 10-bit ADC.

The 4-channel input mux enables multiple composite video signals

to be applied to the ADV7182A and is software controlled.

The next stage in the AFE features the differential to single-

ended converter and the clamp circuitry. The incorporation of a

differential front end allows differential video to be connected

directly to the ADV7182A. The differential front end enables

small and large signal noise rejection, improved electromagnetic

interference (EMI), and the ability to absorb ground bounce.

The architecture can support true differential, pseudo differential,

and single-ended signals.

In conjunction with an external resistor divider, the ADV7182A

provides a common-mode input range of 4 V, facilitating in the

removal of large signal, common-mode transients present on

both video inputs. CMR values of up to 80 dB can be achieved

without the need for external amplifier circuitry.

The external resistor divider is required before each analog

input channel to ensure that the input signal is kept within the

range of the ADC (see Figure 23). Current and voltage clamps

in the circuit attempt to ensure that the video signal remains

within the range on the ADC.

The single 10-bit ADC digitizes the analog video before it is

applied to the SDP. Table 8 shows the three ADC clocking rates

determined by the video input format to be processed. These clock

rates ensure 4× oversampling per channel for CVBS, S-Video, and

YPrPb modes.

Table 8. ADC Clock Rates

Input Format

ADC Clock Rate (MHz)1

Oversampling

Rate per Channel

CVBS

57.27

4×

S-Video (Y/C)2

114

4×

YPrPb2

172

4×

1 Based on a 28.63636 MHz clock input to the ADV7182A.

2 See INSEL[4:0] in Table 96 for writes needed to set S-Video (Y/C) and YPrPb

modes.

STANDARD DEFINITION PROCESSOR

The SDP in the ADV7182A is capable of decoding a large

selection of baseband video signals in composite (both single-

ended and differential), S-Video, and component formats. The

video standards supported by the video processor include PAL B/

PAL D/PAL I/PAL G/PAL H, PAL 60, PAL M, PAL N, PAL Nc,

NTSC M/NTSC J, NTSC 4.43, and SECAM B/SECAM D/

SECAM G/SECAM K/SECAM L. The ADV7182A can automatic-

ally detect the video standard and process it accordingly.

The ADV7182A features a five-line, superadaptive, 2D comb filter

that provides superior chrominance and luminance separation

when decoding a composite video signal. This highly adaptive

filter automatically adjusts the processing mode according to

the video standard and signal quality without requiring user

intervention. Video user controls, such as brightness, contrast,

saturation, and hue, are also available in the ADV7182A.

The ADV7182A implements a patented Adaptive Digital Line

Length Tracking (ADLLT™) algorithm to track varying video

line lengths from sources such as a VCR. ADLLT enables the

ADV7182A to track and decode poor quality video sources,

such as VCRs and noisy sources from tuner outputs, VCD players,

and camcorders. The ADV7182A contains a chroma transient

improvement (CTI) processor that sharpens the edge rate of

chroma transitions, resulting in sharper vertical transitions.

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