STV2118B datasheet(4/25 Pages) STMICROELECTRONICS

4 / 25 page

FUNCTIONAL DESCRIPTION (continued)

2 - FILTERS

- Integrated trap filter :

f−3dB

−

f−3dB

Q = 1.7 at sharp. min

Q = 3.0 at sharp. max

Center frequency : - 4.43MHz,

3.58MHz for PAL, NTSC

- 4.25MHz, for SECAM

(f-3dB = 3 MHz ; -20dB

rejection between 4.1MHz

and 4.4MHz)

- Integrated chroma bandpass :

Q = 3.5

Center frequency : 4.43MHz, 3.58MHz

- Integrated cloche filter for SECAM :

Q= 16

Center frequency : 4.286MHz

- Integrated delay line :

Bandwidth = 8MHz

- Integrated low pass filter for deflection part.

- All filters are tuned with a reference phase locked

loop.

The PLL consists of a lowpass filter, a phase

comparator, a loop filter (an external capacitor).

The reference signal is the continuous carrier

wave from the VCO (4.43MHz or 3.58MHz). The

PLL adjusts the center frequency of the lowpass

so that it is equal to the reference signal. The

tuning voltage of the PLL is used to adjust all other

filters. The cloche filter is fine tuned with a second

PLL operating during frame retrace.

3 - VIDEO CIRCUIT

- 2 RGB inputs : RGB (OSD) input has priority

against the RGBext. Maximum contrast on RGB

(OSD). -12dB range contrast control on RGBext.

Possibility to disable the RGBext insertion

through the bus.

- Oversize blanking capability on FB(OSD)(Pin15)

input. The RGB ouputs will be blanked when the

voltage on Pin 15 will exceed the second thresh-

old at 1.9V (blanking threshold) : the whole field

is blanked but not the inserted cut-off pulses. The

OSD insertion threshold is 0.7V.

- Automatic cut-off current loop : 2V cut-off range.

Sequential cut-off current measurement during

the three lines after the frame blanking signal.

Leakage current measurement during the frame

blanking, memorization on an internal capacitor.

- Possibility to force through the bus the inserted

cut-off pulses on lines 23/24/25(CCIR) in 50Hz

and 60Hz mode.

- Warm up detector.

- Beam current limiter DC voltage input.

The beam current limiter control voltage will act

on contrast first, then the brightness will be de-

creased when contrast attenuationreaches -5dB.

- Bus control of the red, green and blue channel

gain (White point adjustment)

- Bus control of the red and green DC levels (black

point adjustment)

- PAL and SECAM matrix, specific NTSC matrix

when demodulation angles are (0

o,104o).

- Switch-off of the trap filter in SVHS mode.

- Bus controlled contrast on luminance

(20dB range)

- Bus controlled saturation (50dB range)

- Bus controlled brightness : 40% range at maxi-

mum contrast.

- Bus controlled sharpness (peaking) ; sharpness

active in PAL/NTSC standard only.

- Noise coring function on sharpness.

STV2118B

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