a rgb to ntsc/pal encoder with termination switch advanced datasheet AD723 one technology way, p.o. box 9106, norwood. ma 02062-9106, u.s.a. tel: 617/329-4700 fax: 617/326-8703 this information applies to a product under development. its characteristics and specifications are subject to change without notice. analog devices assumes no obligation regarding future manufacture of this product unless otherwise agreed to in writing. rev 2 5/5/98 ordering guide operating model t emperatur e range package AD723ars -40 c - +85 c 24 lead tssop block diagram features composite video output: both ntsc and pal chrominance and luminance (s-video) outputs triple switch to enable rgb termination tv-presence monitor/reporting (supports pc98 sipc) y-trap to eliminate cross color artifacts no external filters or delay lines required current output: 75 w reverse shunt low power +3v operation power down to <100 m a compact tssop applications rgb/vga to ntsc/pal encoding personal computers video games product description the AD723 rgb to ntsc/pal encoders converts red, green and blue color component signals into their corresponding luminance (baseband amplitude) and chrominance (subcarrier amplitude and phase) signals in accordance with either ntsc or pal standards. these two outputs are also combined to provide a composite video output. all three outputs are available separately and are optimized for driving 75-ohm reverse-terminated cables. the AD723 features a logic controlled triple switch which addresses the applications problem of differing load conditions when a rgb monitor is disconnected; when a rgb monitor is not present the r, g and b terminations are enabled by the user. in addition the AD723 monitors and reports the presence of a tv load in support of the pc-98 sipc standard. the AD723 can be powered-down to only 100 ua of current consumption for power sensitive applications. in addition the current-out design of the AD723 eliminates the need for the physically large 220uf capacitors required by other analog encoders, supporting the space constraints of portable applications. an optional luminance trap (ytrap) provides a means of reducing cross color generated by subcarrier frequency components found in the y signal. the AD723 is packaged in a space savings 24 pin tssop and operates from a 3v supply. rin rgnd gin ggnd bin bgnd gnd rgb to yuv encodin g matrix delay u modulator v modulator y trap y cv c ntsc/ pal csync hsync/ csync vsync 4fsc y u v ter minate c lock generator sync /b urst generator d c clamp gnd gnd dc clamp dc clamp chip enable agnd avdd reset 1 reset 2 reset 3 tv direct dghd dvdd
rev 2 5/5/98 page 2 AD723 advanced specifications: unless otherwise stated, v s =+3v, t a = +25 o c. outputs are measured with a 75 w load, shunt reverse termination parameter conditions min typ max units signal inputs (rdin, grin, blin) input amplitude full scale 714 mvp-p black level 1. 0.8 v input resistance 2. red, green, blue 1 m w input capacitance 5 pf logic inputs (sync, fsc, encd, ntsc) cmos logic levels logic lo input voltage 1.0 v logic hi input voltage 2.0 v logic lo input current (dc) < 1 m a logic hi input current (dc) < 1 m a switch characteristics input capacitance vin = 0v 6 pf switch on resistance vin = 0v 3.5 5 w high impedance leakage current 0.1 m a video outputs 3. luminance (luma) roll-off @ 5mhz ntsc -5 db pal - 4 db gain error +5 % linearity error + 0.6 % sync amplitude ntsc 286 mv pal 300 mv dc black level ntsc 338 mv pal 351 mv luminance trap (ytrap) output resistance 1 k w dc black level no load 1.0 v chrominance (crma) bandwidth,-3db passband ntsc 31.2 mhz pal 1.5 mhz color burst amplitude ntsc 286 mvp-p pal 307 mvp-p color signal to burst ratio error 4. 3 % color burst width ntsc 2.51 us pal 2.28 us phase error 5. 3 degrees dc black level 650 mv chroma feedthrough r,g,b = 0 1 0 4 0 mvp-p chroma/luma time alignment error 0 ns composite (cmps) absolute gain error -5 15 % differential gain with respect to chroma 0.5 % differential phase with respect to chroma 2.0 % dc black level ntsc 338 mv pal 351 mv power supplies recommended supply range single supply 3.0 v encode mode quiescent current full white using composite only 45 50 using s-video (y,c) 7 0 7 5 using all three 8 5 9 0 notes: 1. on-chip dc restore requires an external ac-coupling capacitor. 2. except during dc restore (back porch) period. 3. voltages are measured with a 75 w load, and 75 w shunt reverse termination. 4. ratio of chroma amplitude to burst amplitude, difference from ideal. 5. difference between ideal color-bar phases and the actual values.
rev 2 5/5/98 page 3 advanced datasheet AD723 rin rgnd gin ggnd bin bgnd gnd rgb to yuv encodin g matrix timin g generation modulation & filterin g y trap y cv c ntsc/ pal hsync/ csync vsync 4fsc y u v term dc cla mp gnd gnd dc clamp dc cla mp analog rgb encoder with on-chip termination switch AD723 application notes: 1. packaged in 24 pin tssop 2. term inate and ntsc/pal are ttl logic selectable 3. operates from +3v supply 4. rgnd, ggnd and bgnd are to be terminated when rgb m onitor is removed. tv monitor AD723 vga controller r b g rgb monitor ce reset 1 reset 2 reset 3 75 w 75 w 75 w
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