SAF7113 datasheet(13/80 Pages) PHILIPS

13 / 80 page

2000 May 08

Philips Semiconductors

Product speciﬁcation

9-bit video input processor

SAF7113H

+ CLAMP

− CLAMP

NO CLAMP

MGC647

fast

− GAIN

slow

+ GAIN

− GAIN

HCL

HSY

ADC

SBOT

WIPE

CLL

ANALOG INPUT

GAIN ->

<- CLAMP

VBLK

NO BLANKING ACTIVE

Fig.8 Clamp and gain flow.

WIPE = white peak level (254); SBOT = sync bottom level (1); CLL = clamp level [60 Y (128 C)];

HSY = horizontal sync pulse; HCL = horizontal clamp pulse.

8.3

Chrominance processing

The 9-bit chrominance signal is fed to the multiplication

inputs of a quadrature demodulator, where two subcarrier

signals from the local oscillator DTO1 are applied

(0 and 90

° phase relationship to the demodulator axis).

The frequency is dependent on the present colour

standard. The output signals of the multipliers are

low-pass filtered (four programmable characteristics) to

achieve the desired bandwidth for the colour difference

signals (PAL, NTSC) or the 0 and 90

° FM signals

(SECAM).

The colour difference signals are fed to the

Brightness/Contrast/Saturation block (BCS), which

includes the following five functions:

• AGC (automatic gain control for chrominance

PAL and NTSC)

• Chrominance amplitude matching (different gain factors

for (R

− Y) and (B − Y) to achieve ITU-R BT.601 levels

CR and CB for all standards)

• Chrominance saturation control

• Luminance contrast and brightness

• Limiting YUV to the values 1 (minimum) and 254

(maximum) to fulfil ITU-R BT.601 requirements.

The SECAM-processing contains the following blocks:

• Baseband ‘bell’ filters to reconstruct the amplitude and

phase equalized 0 and 90

° FM signals

• Phase demodulator and differentiator

(FM-demodulation)

• De-emphasis filter to compensate the pre-emphasized

input signal, including frequency offset compensation

(DB or DR white carrier values are subtracted from the

signal, controlled by the SECAM switch signal).

The burst processing block provides the feedback loop of

the chrominance PLL and contains:

• Burst gate accumulator

• Colour identification and killer

• Comparison nominal/actual burst amplitude (PAL/NTSC

standards only)

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