ADV7191 datasheet(17/69 Pages) AD

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ADV7190/ADV7191

–17–

REV. 0

FEATURES: FUNCTIONAL DESCRIPTION

BRIGHTNESS DETECT

This feature is used to monitor the average brightness of the

incoming Y signal on a ﬁeld-by-ﬁeld basis. The information is

read from the I

2C and based, on this information, the color

saturation, contrast and brightness controls can be adjusted (for

example to compensate for very dark pictures). (Brightness Detect

CHROMA/LUMA DELAY

The luminance data can be delayed by maximum of six clock

cycles. Additionally the Chroma can be delayed by a maximum

of eight clock cycles (one clock cycle at 27 MHz). (Timing

CHROMA DELAY

LUMA DELAY

Figure 26. Chroma Delay

Figure 27. Luma Delay

CLAMP OUTPUT

The ADV7190/ADV7191 has a programmable clamp TTL

output signal. This clamp signal is programmable to the front

and back porch. The clamp signal can be varied by one to

three clock cycles in a positive and negative direction from the

default position. (Mode Register 5, Mode Register 7.)

CVBS

OUTPUT PIN

CLAMP

OUTPUT PIN

MR57 = 1

MR57 = 0

CLAMP O/P SIGNALS

Figure 28. Clamp Output Timing

CSO, HSO AND VSO OUTPUTS

The ADV7190/ADV7191 supports three output timing sig-

nals,

CSO (Composite Sync Signal), HSO (Horizontal Sync

Signal) and

VSO (Vertical Sync Signal). These output TTL sig-

nals are aligned with the analog video outputs. See Figure 29 for

an example of these waveforms. (Mode Register 7.)

OUTPUT

VIDEO

525

23456789

11–19

EXAMPLE:- NTSC

CSO

HSO

VSO

Figure 29.

CSO, HSO, VSO Timing Diagram

COLOR BAR GENERATION

The ADV7190/ADV7191 can be conﬁgured to generate 100/

7.5/75/7.5 color bars for NTSC or 100/0/75/0 color bars for

PAL. (Mode Register 4.)

COLOR BURST SIGNAL CONTROL

The burst information can be switched on and off the composite

and chroma video output. (Mode Register 4.)

COLOR CONTROLS

The ADV7190/ADV7191 allows the user to control the brightness,

contrast, hue, and saturation of the color. The control regis-

ters may be double-buffered, meaning that any modiﬁcation to

the registers will be done outside the active video region and,

therefore, changes made will not be visible during active video.

Contrast Control

Contrast adjustment is achieved by scaling the Y input data by a

factor programmed by the user. This factor allows the data to be

scaled between 0% and 150%. (Contrast Control Register.)

Brightness Control

The brightness is controlled by adding a programmable setup level

onto the scaled Y data.

For NTSC with pedestal, the setup can vary from 0 IRE to

22.5 IRE. For NTSC without pedestal and PAL, the setup can

vary from –7.5 IRE to +15 IRE. (Brightness Control Register.)

Color Saturation

Color adjustment is achieved by scaling the Cr and Cb input

data by a factor programmed by the user. This factor allows the

data to be scaled between 0% and 200%. (U Scale Register and

V Scale Register.)

Hue Adjust Control

The hue adjustment is achieved on the composite and chroma

outputs by adding a phase offset onto the color subcarrier in the

active video but leaving the color burst unmodiﬁed, i.e., only

the phase between the video and the colorburst is modiﬁed and

hence the hue is shifted. The ADV7190/ADV7191 provides a

range of

± 22° in increments of 0.17578125°. (Hue Adjust

CHROMINANCE CONTROL

The color information can be switched on and off the com-

posite, chroma and color component video outputs. (Mode

UNDERSHOOT LIMITER

A limiter is placed after the digital ﬁlters. This prevents any

synchronization problems for TVs. The level of undershoot is

programmable between –1.5 IRE, –6 IRE, –11 IRE when operat-

ing in 4

× Oversampling. In 2× Oversampling mode the limits are

–7.5 IRE and 0 IRE. (Mode Register 9 and Timing Register 0.)

DIGITAL NOISE REDUCTION

DNR is applied to the Y data only. A ﬁlter block selects the

high frequency, low amplitude components of the incoming

signal (DNR Input Select). The absolute value of the ﬁlter output

is compared to a programmable threshold value (DNR Thresh-

old Control).

Two DNR modes are available: DNR Mode and DNR Sharp-

ness Mode.

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