1 multimedia ics ntsc color tv signal encoder BA7230LS the BA7230LS comprises an rgb signal matrix circuit, balanced modulator circuit (rectangular 2-phase modula- tion), oscillator circuit (vcxo) for a 3.58mhz subcarrier synchronized with video input burst signals, luminosity and color difference signal mixing circuit, and a high speed switch for selecting composite signals of video input and rgb input. rgb signals, synch signals, bfp (burst flag pulses), pcp (pedestal clamp pulses) are input, and an ntsc composite signal is output. applications televisions (teletext-capable), captain systems, video cameras, personal computers features 1) allows superimposition of video images (video in) and computer images (rgb in). 2) during superimposition, the subcarrier locked onto the video input burst signal rgb is modulated with the rgb signals by the apc circuit, preventing unnatural color disturbance due to switching. 3) both the rgb and video input signals are pedestal- clamped, maintaining a natural image even during fluctuation in luminosity. 4) using a half down pulse, the video signal can be reduced by 5db to darken the background and make the superimposed rgb image easier to see. 5) carrier leak is suppressible to less than 70mv p-p (v out = 2v p-p ) without adjustment. 6) can be adapted for analog rgb input. 7) compact 24-pin szip package minimizes external components. block diagram 1 video out 3 y in 5 r-y in 7 v c 9 apc phase adjustment 11 v a 13 ar 15 ab 17 b-y out 19 gnd 21 pcp in 23 y s p in 2 sync in BA7230LS 4 b-y in 6 pd 8 v b 10 burst level adjustment 12 bfp in 14 ag 16 y out 18 r-y out 20 video in 22 hdp in 24 v cc v cc b - y r - y + hd matrix pd vcxo mod mod +
2 multimedia ics BA7230LS input / output circuits 3 2 1 24 23 22 21 20 19 18 17 16 15 12 11 10 9 8 7 6 5 4 clamp clamp 500 w 5.6k w 1k w 9.1k w 10k w 15k w 15k w 7.5k w 15k w 10k w 10k w 500 w 10k w 10k w 1k w 1k w 5.1k w 15k w 10k w 1.2k w 5.1k w 11k w 4.3k w 5k w 6.8k w 1k w gnd 15k w 3.2v 2.2v v cc BA7230LS v cc 3.4v 2.7v 2v 2v 14 13 1k w 6.8k w 1v fig. 1 absolute maximum ratings (ta = 25?) recommended operating conditions parameter symbol limits unit power supply voltage 7.0 v power dissipation 500 * mw operating temperature storage temperature c c ?20 ~ + 70 ?55 ~ + 125 v cc pd topr tstg * reduced by 5.0mw for each increase in ta of 1 c over 25 c. parameter symbol limits unit v cc v 4.5 ~ 5.5 v r v p-p 0 ~ 0.7 v g v p-p 0 ~ 0.7 v b v p-p 0 ~ 0.7 v in v p-p 0 ~ 1.0 power supply voltage r input level g input level b input level video input level
3 multimedia ics BA7230LS electrical characteristics (unless otherwise noted, ta = 25?, v cc = 5.0v) parameter symbol min. typ. max. conditions quiescent current i q ?8 54ma video output level v ov 1.7 2.2 2.6 v p-p video in = 1v p-p half down level change g vh ?3 5 7 db dc offset v of 50 160 mv p-p video in = 1v p-p crosstalk ct 46 ?40 db video in = 1v p-p v r-y 0.3 0.42 0.55 v p-p v b-y 0.2 0.31 0.42 v p-p yout output level v y 1.0 1.4 1.8 v p-p v r = v g = v b = 0.7v p-p ys switching delay time t d 60 ns sync output level v os 0.4 0.65 0.9 v p-p burst output level v ob 0.25 0.46 0.8 v p-p r e = 1.8k w composite output level v oy 1.7 2.2 2.6 v p-p y in = 0.7v p-p g r-y 91113db g b-y 91113db g r-b 2 db difference between above gains ?6 6 deg ?6 6 deg carrier leak l sc ?0 70mv p-p v out = 2v p-p apc capture range f cap 100 hz carrier phase range f sc 30 45 deg superimposition video frequency characteristic f v 4.5 6 mhz ?3db when f = 100khz video output dg dg 3.5 % video in = 1v p-p video output dp dp 2.5 deg video in = 1v p-p z t 815 k w input impedance (ys) z ty 3 7.5 k w v t 0.9 2.0 2.8 v threshold level (ys) v ty 0.5 1.1 1.8 v unit er-ey output level eb-ey output level r-y modulation gain b-y modulation gain (r-y) / (b-y) modulation gain differential (r-y) / (b-y) orthogonal phase shift (r - y) ?urst orthogonal phase shift input impedance (sy, bf, pc, hd) threshold level (sy, bf, pc, hd) v r = 0.7v p-p v b = 0.7v p-p r - y in = 0.3v p-p b - y in = 0.2v p-p burst = 0.1v p-p , 2.8 m s d r d b
4 multimedia ics BA7230LS measurement circuit clamp matrix e r - e y mod pd mod e b - e y bg ?5db 6db v ~ v 0.7v p-p s 1 s 2 s 3 s 4 y out v cc 1 m f 1 m f1 m f 0.047 m f 1 m f 0.047 m f 1 m f 1 m f + 1v p-p s 5 ab 10 m f sync 13 + 14 + 15 2 24 19 16 y in y s v cc 3 23 12 11 1 7 8 9 22 10 20 1 m f + 5 1 m f + 4 b - y BA7230LS 6db r - y 21 pcp video 6 hdp tc x'tal bfp 2.7k w 75 w vector scope oscilloscope 75 w 820 w 82pf 560 w 1.8k w 68pf 470 w 10k w 1.2k w + + + 18 r - y ~ i cc + + vcxo bg 1k w 1k w 75 w 75 w y 17 b - y + ~~ v fig. 2 10k s6
5 multimedia ics BA7230LS clamp matrix e r - e y mod pd mod ?5db rg b r 1 c 1 r 2 r 3 c 17 v cc (5v) c 16 y out r 4 dl 1 16 + 1 m f 1 m f rgb video 0.047 m f 1 m f + r 15 c 9 in 1k w bfp vr 4 v cc v cc vr 3 vr 2 c 11 q 1 c 12 33pf 20pf c 13 1.2 mh l 1 r 16 1k w 2sc2021 c 10 q 2 2sc2021 burst level adj 10 m f 0.047 m f sync 13 + 14 + 15 2 24 19 gnd 1k w r 5 y s r 6 dl 2 r 7 1k w 1k w 1k w dly (400ns) trp (3.58m) dly y in v cc vr 1 v cc r 6 r 13 r 14 tc 1 q 3 r 10 r 11 r 9 c 19 r 12 2.7k c 6 1 m 0.047 m f c 15 c 7 c 8 c 5 aps phase adj 3 23 11 12 out composite 7 8 9 22 10 20 1 m f + 5 1 m f + 4 17 BA7230LS b - y y r - y 18 6db 6db y 21 pcp video 6 10k w + 75 w 1.2k w out 2sc2021 820 w x'tal 1 10pf 82pf 560 w hdp 0db ?5db 560 w 5k w 3k w 300 w 3k w 300 w 68pf 470 w 10k w + + 560 w 560 w + + (2v p-p ) bg vcxo c 14 33pf 20pf c 15 l 2 lpf r 17 1k w e b - e y 1.2mh c 4 dl 1 , dl 2 : x503 (sumida) l 1 , l 2 : rc-875 1.2mh (sumida) tc 1 : tz03r200e (murata) q 1 , q 2 , q 3 : 2sc2021 (rohm) xtal 1 : hc ?43u 3579.545khz (nikko denshi) bg fig. 3 application example
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 e y , e r -e y and e b -e y by the resistance-adding matrix circuit. e y = 0.30e r + 0.59e g + 0.11e b e r ?e y = 0.70e r ?0.59e g ?0.11e b e b ?e y = ?0.30e r ?0.59e g + 0.89e b signal e y 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 e r -e y is output at 1 / 1.14 and signal e b -e y 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 e y' (to which a horizontal syn- chronization signal is added) to create the ntsc com- posite signal (e n ). (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 w 5.1k w 27k w BA7230LS y fig. 4 out y s rgb composite video in fig. 6 r 14 560 w c 6 68pf c 7 82pf 9 tc 1 20pf r 13 1.2k w xt 1 3.58mhz 87 vcxo fig. 7 video in hdp (half down pulse) out y s rgb composite ?5db fig. 8 amplitude r - y r - y b - y e b - e y 3.58mhz (0 ) c carrier color signal (combining of r-y and b-y) b - y q m s 90 q 90 time 1 3.58 balanced modulator e r - e y carrier color signal 3.58mhz (90 ) balanced modulator + fig. 5 e n = e y' + cos2 p fst e r ?e y 1.14 + sin2 p fst e b ?e y 2.03
7 multimedia ics BA7230LS video in sync v h 1v p-p v l ttl level ( * 1) pcp v h v l ttl level ( * 1) v h v l ttl level ( * 1) rgb in v l v l 0.7v p-p hdp v h ttl level ( * 1) y s v h ttl level ( * 2) cb from rgb composite out 2v p-p cb super impose cb: color burst * 1 v l : 0 ~ 0.8v v h : 3.0v ~ v cc * 2 v l : 0 ~ 0.4v v h : 2.0v ~ v cc 2v p-p cb bfp fig. 9 input waveform and timing chart electrical characteristic curves 80 70 60 50 40 30 20 10 quiescent current: i q (ma) 0 012345 power supply voltage: v cc (v) 6 78 fig. 10 quiescent current vs. power supply voltage 3580.5 f 0 = 3579.545khz 3580.0 3579.5 3579.0 frequency: f (free run) (khz) 3578.5 345 power supply voltage: v cc (v) 6 7 fig. 11 vcxo free-run frequency vs. power supply voltage f 0 = 3579.545khz v in = 0.1v p-p + lock + cap 400 600 200 f 0 = 0 ?200 ?400 ?600 frequency: f (cap. lock) (hz) 34 5 power supply voltage: v cc (v) 6 7 ?cap ?lock fig. 12 capture range and lock range ( ! ) vs. power supply voltage
8 multimedia ics BA7230LS szip24 5.8 0.2 9.9 0.5 0.889 1 2 23 24 0.5 0.1 + 0.1 ?0.05 2.54 0.25 0.3 2.0min. 21.8 0.2 2.8 0.2 operation notes (1) rgb and video inputs should be synchronized. when only rgb is input, connect video in (pin 20) to gnd with a 1 m f capacitor, and synchronize pcp and bfp to rgb. (3) input pins with pedestal clamps cannot be left open and must be grounded with a low impedance. when not used, ground with a 1 m f capacitor. * input pins with pedestal clamps: y in (pin 3), b-y in (pin 4), r-y in (pin 5), video in (pin 20) (2) the vcxo remains in a free-running state except during superimposition. (4) pin 4 (b-y in ) and pin 5 (r-y in ) have high imped- ance and are susceptible to the effects of noise and other external factors dur- ing pattern generation. for this reason, we recom- mend adding the circuit in fig. 15 to lower the input impedance. adding this cir- cuit can also reduce carrier leakage. 1 m f 1 m f 1k w fig. 14 + + c 12 33pf 20pf c 13 l 1 r 16 1k w 18 c 14 33pf 20pf c 15 1.2mh lpf 0.5mhz l 2 r 17 1k w 17 4 v cc q 1 q 1 , q 2 : 2sc2021 (rohm) 3k w v cc q 2 c 10 c 11 3k w 300 w 1 m f 1 m f + + 300 w 5 1.2mh fig. 15 additional circuit + lock + cap 400 600 200 f 0 = 0 ?200 ?400 ?600 frequency: f (cap. lock) (hz) 0 200 400 input voltage: v in (mv p-p ) 600 700 500 300 100 800 ?cap ?lock f 0 = 3579.545khz v cc = 5v fig. 13 capture range and lock range ( @ ) vs. input voltage external dimensions (units: mm)
|
