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BA7230LS 数据表(PDF) 6 Page - Rohm |
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BA7230LS 数据表(HTML) 6 Page - Rohm |
6 / 8 page 6 Multimedia ICs BA7230LS •Circuit operation (1) Matrix circuit The R, G and B inputs are clamped to 3.2V by the clamp circuit and combined into signals EY, ER-EY and EB-EY by the resistance-adding matrix circuit. EY = 0.30ER + 0.59EG + 0.11EB ER – EY = 0.70ER – 0.59EG – 0.11EB EB – EY = – 0.30ER – 0.59EG + 0.89EB Signal EY is then amplified by the 6dB amplifier (pin 16) to compensate for the signal's 6dB attenuation in the delay line. To prevent overmodulation, signal ER-EY is output at 1 / 1.14 and signal EB-EY at 1 / 2.03 (pins 17 and 18). (2) Balanced modulator circuit Color difference signals are modulated (rectangular 2- phase balanced modulation) with color subcarriers (3.58MHz) having a 90° phase difference. This is called the carrier color signal. The carrier color signal is mixed with color burst signals and luminosity signals EY' (to which a horizontal syn- chronization signal is added) to create the NTSC com- posite signal (EN). (3) Switch circuit Signal Ys (pin 23) switches between video input and RGB composite signals. Performing this switching at high speeds results in superimposition. (4) Color subcarrier oscillator circuit The subcarrier oscillator circuit for RGB input. This cir- cuit is synchronized with the video input color burst sig- nal extracted by BFP (burst flag pulses) during super- imposition, preventing any unnatural color disturbance due to switching between RGB and video input. This oscillator circuit generates the RGB color burst signal. An attached variable resistor can be used to change the amplitude of the color burst signal and to adjust its phase relative to the video color burst signal. This oscillator circuit remains in the free-running state when there is no video input. (5) During superimposition, video input can be lowered by about 5dB using an HDP (half-down pulse), darken- ing the background and making RGB input easier to see. 13 R 14 G 15 B 10k Ω 5.1k Ω 27k Ω BA7230LS Y Fig. 4 OUT YS RGB COMPOSITE VIDEO IN Fig. 6 9 TC1 20pF R13 1.2k Ω XT1 3.58MHz 87 VCXO Fig. 7 VIDEO IN HDP (Half Down Pulse) OUT YS RGB COMPOSITE – 5dB Fig. 8 R - Y R - Y B - Y EB - EY 3.58MHz (0 °) C carrier color signal (combining of R-Y and B-Y) B - Y θ µs 90 ° θ 90 ° Time 1 3.58 Balanced modulator ER - EY Carrier color signal 3.58MHz (90 °) Balanced modulator + Fig. 5 EN = EY' + cos2 πfst ER – EY 1.14 + sin2 πfst EB – EY 2.03 |
类似零件编号 - BA7230LS |
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类似说明 - BA7230LS |
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