STV2246H STMicroelectronics, STV2246H Datasheet - Page 23

• Manufacturer Part Number: STV2246H
• Manufacturer: STMicroelectronics

Specifications of STV2246H

• Lead Free Status / Rohs Status: Compliant

STV224X, STV228X, STV223X - FUNCTIONAL DESCRIPTION
3.3.4 Integrated Luma Delay Line
Bandwidth: 8 MHz.
The Luma Delay Line is automatically adapted to
the chroma standard. For PAL BG and applica-
tions without group delay compensation, a Luma
Delay Shift of -140 ns can be selected via the I²C
bus.
3.3.5 Filter Tuning
All filters are tuned via a reference phase-locked
loop. The PLL is based on a trap filter, a phase
comparator and an internal loop filter (capacitor).
The reference signal is the continuous carrier
wave from the Chroma VCO (4.43 MHz or
3.58 MHz). The PLL adjusts the center frequency
of the trap until it equals the reference signal.The
PLL tuning voltage is used to adjust all other inte-
grated filters. The Bell filter is fine-tuned with a
second PLL during the frame retrace. The Bell fil-
ter tuning voltage is memorized on an external ca-
pacitor (BTUN Pin).
3.4 VIDEO CIRCUIT
3.4.1 RGB Inputs
The RGB (OSD) input has priority over the exter-
nal RGB input. The RGB (EXT) source is matrixed
into YUV signals for color and contrast adjust-
ments. The brightness is adjusted according to the
internal and external RGB and OSD RGB signals.
The Contrast Control regulates both external and
internal RGB signals and has a maximum attenua-
tion of -24 dB. It also regulates the OSD RGB sig-
nal and its maximum attenuation is limited to
-12 dB. The Contrast Control for RGB (OSD) input
can be disabled via the bus. The brightness of the
RGB (OSD) input varies according to the main
brightness level.
The RGB (EXT) insertion signal can be disabled or
forced via the bus. A fast blanking detector on the
external fast blanking input is able to detect the
Fast Blanking pulse occurrence at each frame and
then memorizes it until the end of the next frame.
RGB Insertion is controlled either by an external
signal on the FBEXT pin or via the I²C bus. The
Fast Blanking detection status is sent to the I²C
bus read register.
3.4.2 YCrCb Mode
External YCrCb signals can be applied to RGB
(EXT) inputs. Two input modes are possible:
– The Sync signal is applied to CVBS input, the Y
– The Y signal is applied to CVBS input, the Cr sig-
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signal is applied to GEXT, the Cr signal is applied
to REXT and the Cb signal is applied to BEXT.
nal is applied to REXT and the Cb signal is ap-
The OSD fast blanking input has several functions:
OSD Insertion Control, RGB Output Blanking or
Half Contrast Control.
3.4.3 Half-Contrast Control
A 6 dB gain reduction will be applied to the internal
YUV signals when the half-contrast function is
turned ON, and the voltage of the half-contrast in-
put exceeds the threshold (0.7 V Typ.).
The Half Contrast input is combined with the
FBOSD input.
3.4.4 YUV to RGB Matrix
The PAL/SECAM matrix is provided and a specific
NTSC matrix is used when demodulation angles
are (0°,104°).
3.4.5 Automatic Cut-off Current Loop
The Cut-off Loop range is 2 V (the cut-off level of
the RGB outputs is between 1.5 V and 3.5 V,
2.5 V Typ.). The cut-off current is measured se-
quentially during the three lines after the internal
frame blanking signal (the blue cathode current is
measured first, then the green and red). The Leak-
age cathode current is measured during frame
blanking and is memorized on an internal capaci-
tor. The Cut-off loop can be frozen via the bus. To
prevent cut-off lines from being visible in 16:9
mode, cut-off pulses are not inserted when the cut-
off loop is frozen.
3.4.6 Warm-up Detector
At power on, the cut-off loop is not active and high
DC levels are inserted during "cut-off" lines. The
Cut-off loop will be active when the cathode cur-
rent reaches the warm-up detection threshold.
This causes the picture to be displayed from a
dark screen. The RGB outputs are blanked until
cut-off current is close to the reference voltage.
The manual cut-off mode can be selected via the
I²C bus. In this mode, the I
tive and cut-off pulses are not inserted. The RGB
black levels are independently controlled by three
I²C bus registers (8-bit resolution). The black level
of each RGB output can be adjusted within a
range of 2.5 V (typ.).
3.4.7 Beam Current Limiter DC Voltage Input
The Beam Current Limiter (BCL) will first decrease
the contrast and then the brightness when the
contrast attenuation reaches -5 dB.
3.4.8 Drive (RGB gain) and DC Adjustment
The red, green, blue channel gain for white point
adjustment takes place via the bus. The red and
plied to GEXT. The trap and luma delay line must
be disabled by the I²C bus and peaking must be
set to minimum.
CATH
input pin is inac-