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STV223X Datasheet(PDF) 23 Page - STMicroelectronics |
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STV223X Datasheet(HTML) 23 Page - STMicroelectronics |
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23 / 86 page  STV224XH/228XH/223XH - FUNCTIONAL DESCRIPTION 23/86 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 signal is applied to GEXT, the Cr signal is applied to REXT and the Cb signal is applied to BEXT. – The Y signal is applied to CVBS input, the Cr sig- nal is applied to REXT and the Cb signal is ap- plied to GEXT. The trap and luma delay line must be disabled by the I²C bus and peaking must be set to minimum. 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 ICATH input pin is inac- 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 |
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