SONY BG2T CHASSIS
Owner's Manual

� 14 �

Chapter 6 VIDEO PROCESSING CIRCUIT
6.1 Description The Y/C Jungle IC, TDA8843 and TDA8844 are I2C bus controlled single chip TV processors which are intended to be applied in PAL, NTSC, PAL/ NTSC and multi standard television receivers.This processor is equipped with alignment-free IF PLL demodulator with internal VCO. Also the setting of various IF frequencies (33.4,33.9,38, 38.9, 45.75 and 58.75 MHz) can be made via the I2C bus. Features of Y/C Jungle IC - Multi-standard IF circuit with an alignment-free PLL demodulator without external components - Alignment-free multi standard FM sound demodulator (4.5 MHz to 6.5 MHz) - Flexible source selection with CVBS switch and Y(CVBS)/C input so that a comb filter can be applied. - Integrated chrominance trap circuit - Integrated luminance delay line - Asymmetrical peaking in the luminance channel with a (defeatable) noise coring function. - Black stretching of non-standard CVBS or luminance signals. - Integrated chroma band-pass filter with switchable centre frequency - Dynamic skin tone control circuit - Blue stretch circuit which offsets colours near white towards blue - RGB control circuit with �Continous Cathode Calibration� and white point adjustment - Horizontal synchronization with two control loops and alignment-free horizontal oscillator - Vertical count-down circuit - Vertical driver optimised for DC-coupled vertical output stages - I2C bus control of various functions. 6.2 Functional Description Chroma and luminance processing The TDA8843 and TDA8844 contain a chroma bandpass and trap circuit.The filters are realised by means of gyrator circuits and they are automatically

calibrated by comparing the tuning frequency with the X-tal frequency of the decoder. The centre frequency of the chroma bandpass filter is switchable via the I2C. During SECAM reception the centre frequency of the chroma trap is reduced to get a better suppression of the SECAM carrier frequencies. Colour Decoder Depending on the IC type, the colour decoder can decode PAL/NTSC or PAL/NTSC/SECAM signals. The PAL/NTSC decoder contains an alignment-free Xtal oscillator, a killer circuit and two colour difference demodulators. The IC�s contain an Automatic Colour Limiting (ACL) circuit which is switchable via the I 2C bus. This features help preventing oversaturation occurs when signals with a high chroma to burst ratio are received. The ACL circuit is designed such that it only reduces the chroma signal and not the burst signal. This has the advantage that colour sensitivity is not affected by this function. The IC�s also contain �Dynamic skin tone (flesh) control� feature. This function is realised in the YUV domain by detecting the colours near to the skin tone. The correction is depend on the luminance , saturation and the correction angle can be controlled via the I2C bus. Sound Circuit The sound bandpass and trap filters have to be connected externally.The filtered intercarrier signal is fed to a limiter circuit and is demodulated by means of a PLL demodulator. This PLL circuit tunes itself automatically to the incoming carrier signal so that no adjustment is required. The volume is controlled via the I2C-bus. This function can be used to switch-off the sound during a channel change so that high output peaks prevented. For multi system (B/G,I,D/K and M),serial buffers (Q313,Q312,Q310,Q308), switches (Q311,Q309,Q307,Q306) together with ceramic traps (CT345,CT355,CT360,CT365) and filters (CF345,CF355,CF360,CF365) incoorperate with the Y/C jungle and microcontroller to fullfill this function.The IF V OUT from pin6 will transform to respective system of SIF accordingly by this stage.