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april 1997 preliminary ML6421 triple phase and sinx/x equalized, low-pass video filter 1 block diagram triple input/anti-aliasing video filter 15 5 6 4 buf 1x/2x buf low pass filter a v in a 10 v out a 3k w 1k w 3.33k w 16 1 buf low pass filter b v in b 9 3 v out b 3.33k w 2 14 buf low pass filter c v in c 7 v out c 3.33k w v cc c 8 v cc b v cc 11 v cc a gndc 13 gnda 12 gnd gnd range gndb i bias i bias i bias 3k w 1k w 3k w 1k w sinx/x equalizer sinx/x equalizer sinx/x equalizer all pass filter all pass filter all pass filter 1x/2x buf 1x/2x buf general description the ML6421 monolithic bicmos 6th-order filter provides fixed frequency low pass filtering for video applications. this triple phase-equalized filter with sinx/x correction is designed for reconstruction filtering at the output of a video dac. cut-off frequencies are either 5.5, 8.0, 3.0 or 1.8mhz. each channel incorporates a 6th-order lowpass filter, a first order all-pass filter, a gain boost circuit, and a 75y coax cable driver. a control pin (range) is provided to allow the inputs to swing from 0 to 1v, or 0.5 to 1.5v, by providing a 0.5v offset to the input. the unity gain filters are powered from a single 5v supply, and can drive 1v p-p over 75y (0.5v to 1.5v), or 2v p-p over 150y (0.5v to 2.5v) with the internal coax drivers. features n 5.5, 8.0, 9.3, 3.0, 1.8 or 2.5mhz bandwidth n 1x or 2x gain n 6th-order filter with phase and amplitude equalizer n >40db stopband rejection n no external components or clocks n 10% frequency accuracy over maximum supply and temperature variation n <2% differential gain <2 differential phase n <25ns group delay variation n drives 1v p-p into 75 w , or 2v p-p into 150 w n 5v 10% operation 1x gain 2x gain ml6201-1 ML6421-2 ML6421-3 ML6421-4 ML6421-5 ML6421-6 ML6421-7 ML6421-8 filter a 5.5mhz 5.5mh 8.0mhz 8.0mhz 5.5mhz 5.5mh 9.3mhz 9.3mhz filter b 5.5mhz 1.8mh 8.0mhz 3.0mhz 5.5mhz 2.5mh 9.3mhz 3.3mhz filter c 5.5mhz 1.8mh 8.0mhz 3.0mhz 5.5mhz 2.5mh 9.3mhz 3.3mhz
ML6421 2 pin configuration pin description pin name function 1 gndb ground pin for filter b. 2v in c signal input to filter c. input impedance is 4k w . 3 gnd power and logic ground. 4 gndc ground pin for filter c. 5v cc positive supply. 6v cc c power supply for filter c. 7v out c output of filter c. drive is 1v p-p into 75 w (0.5v to 1.5v), or 2v p-p into 150 w (0.5v to 2.5v). 8v cc b power supply for filter b: 4.5v to 5.5v. 9v out b output of filter b. drive is 1v p-p into 75 w (0.5v to 1.5v), or 2v p-p into 150 w (0.5v to 2.5v). 10 v out a output of filter a. drive is 1v p-p into 75 w (0.5v to 1.5v), or 2v p-p into 150 w (0.5v to 2.5v). pin name function 11 v cc a power supply for filter a. 12 gnd power and logic ground. 13 gnda ground pin for filter a. 14 range input signal range select. for -1 to -4; when range is low (0), the input signal range is 0.5v to 2.5v, with an output range of 0.5v to 2.5v. when range is high (1), the input signal range is 0v to 2v, with an output range of 0.5v to 2.5v. for -5 to -8; when range is low (0), the input signal range is 0.5v to 1.5v, with an output range of 0.5v to 2.5v. when range is high (1), the input signal range is 0v to 1v, with an output range of 0.5v to 2.5v. 15 v in a signal input to filter a. input impedance is 4k w . 16 v in b signal input to filter b. input impedance is 4k w . 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 top view ML6421 16-pin wide soic (s16w) gndb v in c gnd gndc v cc v cc c v out c v cc b v in b v in a range gnda gnd v cc a v out a v out b
ML6421 3 absolute maximum ratings absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device operation is not implied. supply voltage (v cc ) ..................................... C0.3 to +7v gnd .................................................. C0.3 to v cc +0.3v logic inputs ........................................ C0.3 to v cc +0.3v input current per pin ............................................ 25ma storage temperature ................................... C65 to 150c package dissipation at t a = 25c .............................. 1w lead temperature (soldering 10 sec) ...................... 150c thermal resistance ( q ja ) ..................................... 65c/w operating conditions supply voltage ................................................. 5v 10% temperature range .................................. 0c < to < 70c electrical characteristics unless otherwise specified v cc = 5v 10% and t a = t min to t max , r l =75y or 150y, v out = 2v p-p for 150y load and v out = 1v p-p for 75y load (note 1) symbol parameter conditions min typ max units general r in input impedance 3 4 5 k y d r/r in input r matching 2 % i bias input current v in = 0.5v, ML6421(-1 to -4) C80 a range = low ML6421(-5 to -8) 45 a v in = 0.0v, ML6421(-1 to -4) C125 a range = high ML6421(-5 to -8) C210 a small signal gain v in = 100mv p-p ML6421(-1 to -4) C0.5 0 0.5 db at 100khz ML6421(-5 to -8) 5.5 6 6.5 db differential gain v in = 1.1v to 2.5v ML6421 (-1 to -4) 1 2 % at 3.58 & 4.43 mhz v in = 0.8v to 1.5v ML6421 (-5 to -8) 1 2 % at 3.58 & 4.43 mhz differential phase v in = 1.1v to 2.5v ML6421 (-1 to -4) 1 2 deg at 3.58 & 4.43 mhz v in = 0.8v to 1.5v ML6421 (-5 to -8) 1 2 deg at 3.58 & 4.43 mhz v in input range range = 0 ML6421(-1 to -4) 0.5 2.5 v ML6421(-5 to -8) 0.5 1.5 v range = 1 ML6421(-1 to -4) 0.0 2.0 v ML6421(-5 to -8) 0.0 1 v peak overshoot 2t, 0.7v p-p pulse 2.0 % crosstalk rejection f in = 3.58, ML6421(-1 to -4) 50 db f in = 4.43mhz ML6421(-5 to -8) 45 db (note 6) channel to channel f in = 100khz 20 ns group delay matching (f c = 5.5mhz) channel to channel f in = 100khz 4 % gain matching output current r l = 0 (short circuit) 175 ma
ML6421 4 electrical characteristics (continued) symbol parameter conditions min typ max units general (continued) c l load capacitance 35 pf composite chroma f c = 5.5mhz ML6421(-1 to -4) 20 ns /luma delay ML6421(-5 to -8) 25 ns f c = 8.0mhz/9.3mhz 5/8 tbd ns 5.50mhz filter (ML6421-1, -5) bandwidth C0.75db (note 5) ML6421(-1 to -4) 4.95 5.50 6.05 mhz (monotonic passband) C0.55db (note 5) ML6421(-5 to -8) 4.95 5.50 6.05 mhz subcarrier frequency gain f in = 3.58mhz ML6421(-1 to -4) C0.3 0.2 0.7 db ML6421-1 or ML6421-2 ML6421(-5 to -8) C0.9 1.4 1.9 db f in = 4.43mhz ML6421(-1 to -4) C0.35 0.1 0.65 db ML6421(-5 to -8) 1.1 1.6 2.1 db attenuation f in = 10mhz ML6421(-1 to -4) 16 18 db ML6421(-5 to -8) 20 25 db f in = 50mhz 40 45 db output noise bw = 30mhz (note 6) 1000 v rms group delay 145 ns 8.0mhz filter bandwidth C3db (note 5) 7.2 8 8.8 mhz (monotonic passband) subcarrier frequency gain f in = 3.58mhz C0.25 0.25 0.75 db ML6421-3 or ML6421 f in = 4.43mhz C0.11 0.39 0.89 db 4/ML6421-7 or ML6421-8 attenuation f in = 17mhz 20 25 db f in = 85mhz 40 42 db output noise bw = 30mhz (note 6) 1000 v rms group delay 120 ns 9.3mhz filter bandwidth C2db (note 5) 8.4 9.3 10.2 mhz (monotonic passband) subcarrier frequency gain f in = 3.58mhz C0.01 0.4 0.9 db ML6421-3 or ML6421 f in = 4.43mhz C0.1 0.6 1.1 db 4/ML6421-7 or ML6421-8 attenuation f in = 17mhz 20 25 db f in = 85mhz 40 42 db output noise bw = 30mhz (note 6) 1000 v rms group delay 120 ns
ML6421 5 electrical characteristics (continued) symbol parameter conditions min typ max units 3.3mhz filter bandwidth C2.5db (note 5) 2.7 3 3.3 mhz (monotonic passband) attenuation f in = 9.82mhz 30 33 db f in = 60mhz 43 50 db output noise bw = 30mhz (note 6) 700 v rms bandwidth C2db (note 5) 3 3.3 3.6 mhz (monotonic passband) attenuation f in = 9.82mhz 30 33 db f in = 60mhz 43 50 db output noise bw = 30mhz (note 6) 700 v rms 1.8mhz filter bandwidth C2db (note 5) 1.65 1.8 2.0 mhz (monotonic passband) attenuation f in = 4.91mhz 26 28 db f in = 30mhz 43 50 db output noise bw = 30mhz (note 6) 700 v rms group delay 300 ns 2.5mhz filter bandwidth C2.15db (note 5) 2.25 2.5 2.75 mhz (monotonic passband) attenuation f in = 4.91mhz 18 23 db f in = 30mhz 40 45 db output noise bw = 30mhz (note 6) 700 v rms group delay 300 ns digital and dc v il logic input low range 0.8 v v ih logic input high range v cc C 0.8 v i il logic input low v in = gnd C1 a i ih logic input high v in = v cc 1a i cc supply current v in = 0.5v (note 4) 110 135 ma r l = 75y v in = 1.5v 140 175 ma note 1: limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. note 2: maximum resistance on the outputs is 500y in order to improve step response. note 3: connect all ground pins to the ground plane via the shortest path. note 4: power dissipation: p d = (i cc v cc ) C [3(v out 2 /rl)] note 5: the bandwidth is the C3db frequency of the unboosted filter. this represents the attenuation that results from boosting the gain from the C3db point at the specified frequency. note 6: these parameters are guaranteed by characterization only.
ML6421 6 figure 1a. stop-band amplitude vs frequency (f c = 5.5mhz). 10 0 C10 C20 C30 C30 C40 C50 C60 C70 C80 C90 amplitude (db) frequency (hz) 100k 1m 10m 100m figure 2a. pass-band amplitude vs frequency (f c = 5.5mhz). 2 1 0 C1 C2 C3 C4 C5 C6 C7 C8 relative amplitude (db) frequency (hz) 100k 1m 10m ml6420-5 ML6421-5 10 0 C10 C20 C30 C30 C40 C50 C60 C70 C80 C90 amplitude (db) frequency (hz) 100k 1m 10m 100m figure 1d. stop-band amplitude vs frequency (f c = 3.0mhz). 10 0 C10 C20 C30 C30 C40 C50 C60 C70 C80 C90 amplitude (db) frequency (hz) 100k 1m 10m 100m figure 1b. stop-band amplitude vs frequency (f c = 1.84mhz). 10 0 C10 C20 C30 C30 C40 C50 C60 C70 C80 C90 amplitude (db) frequency (hz) 100k 1m 10m 100m figure 1c. stop-band amplitude vs frequency (f c = 8.0mhz). figure 2b. pass-band amplitude vs frequency (f c = 9.3mhz). 2 1 0 C1 C2 C3 C4 C5 C6 C7 C8 relative amplitude (db) frequency (hz) 100k 1m 10m ml6420-7 ML6421-7
ML6421 7 group delay (ns) f requency (mhz) ML6421-1 ML6421-5 220 210 200 190 180 170 160 150 140 23456 7 figure 3a. group delay vs frequency (f c = 5.5mhz). 318 308 298 288 278 268 258 248 238 228 218 group delay (ns) frequency (hz) 100k 2mhz 4mhz figure 3b. group delay vs frequency (f c = 1.84mhz). group delay (ns) frequency (mhz) ML6421-3 ML6421-7 12 34 56 7891011 140 130 120 110 100 90 figure 3c. group delay vs frequency (f c = 8.0mhz). 232 222 212 202 192 182 172 162 152 142 132 group delay (ns) frequency (hz) 100k 3.5mhz 7mhz figure 3d. group delay vs frequency (f c = 3.0mhz).
ML6421 8 functional description the ML6421 single-chip triple video filter ic is intended for consumer and low cost professional video applications. each of the three channels incorporates an input buffer amplifier, a sixth order lowpass filter, a first order allpass equalizer, sinx/x equalizer and an output amplifier capable of driving 75y to ground. the ML6421 can be driven by a dac with range down to 0v. when range is low the input and output signal range is 0.5v to 2.5v. when the input signal includes 0v, range should be tied high. in this case, an offset is added to the input so that the output swing is kept between 0.5v to 2.5v. the output amplifier is capable of driving up to 24ma of peak current; therefore the output voltage should not exceed 1.8v when driving 75y to ground. application guidelines output considerations the triple filters have unity gain. the circuit has unity gain (0db) when connected to a 150y load, and a C6db gain when driving a 75y load via a 75y series output resistor. the output may be either ac or dc coupled. for ac coupling, the C3db point should be 5hz or less. there must also be a dc path of -500y to ground for output biasing. input considerations the input resistance is 4ky. the input may be either dc or ac coupled. (note that each input sources 80 to 125a of bias current). the ML6421 is designed to be directly driven by a dac. for current output video dacs, a 75y or 150y resistor to ground may need to be added to the dac output (filter input). figure 4. ML6421 ac coupled dc bias test circuit 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 v in b v in a range gnda gnd v cc a v out a v out b gndb v in c gnd gndc v cc v cc c v out c v cc b 75 w 75 w outa outb 1 m f 0.1 m f 0.1 m f 100 m f 100 m f 3.1k w 47 w 1k w 85 w 47 w 85 w 3.1k w 1k w inb ina 0.1 m f 100 m f 1nf 1nf 1nf 1nf 0.1 m f 0.1 m f 0.1 m f 0.1 m f 0.1 m f 0.001 m f 1 m f 100 m f 75 w 85 w 47 w outc 3.1k w 1k w inc +5v fb2 fb1 dc bias input signal = 2v p-p input decoupling supply noise clamping input termination 1 m f
ML6421 9 layout considerations in order to obtain full performance from these triple filters, layout is very important. good high frequency decoupling is required between each power supply and ground. otherwise, oscillations and/or excessive crosstalk may occur. a ground plane is recommended. each filter has its own supply and ground pins. in the test circuit, 0.1f capacitors are connected in parallel with 1nf capacitors on v cc , v cc c, v cc b and v cc a for maximum noise rejection (figure 4). further noise reduction is achieved by using series ferrite beads. in typical applications, this degree of bypassing may not be necessary. since there are three filters in one package, space the signal leads away from each other as much as possible. power considerations the ML6421 power dissipation follows the formula: p(i v) v rl 3 dcccc out 2 = - ? ? ? ? ? ? ? this is a measure of the amount of current the part sinks (current in C current out to the load). under worst case conditions: pmw d =- ? ? ? ? ? ? = (. .) . . 0 175 5 5 15 75 3 872 5 2 ML6421 video low pass filter filter selection: the ML6421 provides several choices in filter cut-off frequencies depending on the application. rgb: when the bw of each signal is the same, then the ML6421-1 (5.5mhz) or ML6421-3 (8mhz) are appropriate depending on the sampling rate. yuv: when the luminance bandwidth is different from the color bandwidth, then the ML6421-2 5.5mhz filter with two 1.8mhz filters and the ML6421-4 with the 8.0, and two 3.0mhz filters are most appropriate. the 1.8mhz filter provides a narrower bandwidth for optimal data compression (with mpeg and other compression schemes), and has a time digital delay of 3.5 clock clycles at 13.5mhz for simple digital delay compensation. s-video: for y/c (s-video) and y/c + cv (composite video) systems the 5.5mhz or 8mhz filters are appropriate. in ntsc the c signal occupies the bandwidth from about 2.6mhz to about 4.6mhz, while in pal the c signal occupies the bandwidth from about 3.4mhz to about 5.4mhz. in both cases, a 5.5mhz low pass filter provides adequate rejection for both sampling and reconstruction. in addition, using the same filter for both y/c and cv maintains identical signal timing without adjustments. composite: when one or more composite signals need to be filtered, then the 5.5mhz and 8mhz filters permit filtering of one, two or three composite signals. over sampling: while the ML6421 filters can eliminate the need for over sampling combined with digital filtering, there are times when over sampling is used. for these situations, 8mhz could be used in place of 5.5mhz, and 3.0mhz could be used in place of 1.8mhz. ntsc/pal: a 5.5mhz cut-off frequency provides good filtering for 4.2mhz, 5.0mhz and 5.5mhz signals without the need to change filters on a production basis. sinx/x: for digital video system with output d/a converters, there is a fall-off in response with frequency due to discrete sampling. the fall-off follows a sinx/x response. the ML6421 filters have a complementary boost to provide a flatter overall response. the boost is designed for 13.5mhz y/c and cv sampling and 6.75mhz u/v sampling. note: the ML6421 has the same pin-out as the ml6420. in a typical application the ML6421 is used as the final output device in a video processing chain. in this case, inputs to the ML6421 are supplied by dac outputs with their associated load resistors (typically 75y or 150y). resistance values should be adjusted to provide 2v p-p at the input of the ML6421. the ML6421 will drive 75y source termination resistors (making the total load 150y) so that no external drivers or amplifiers are required. 4 2 0 C2 C4 amplitude frequency (mhz) 01234567 theoretical sinx/x correction for 13.5mhz sampling sinx/x error for typical dac at 13.5mhz figure 5a. sinx/x frequency response
ML6421 10 figure 6. ML6421 reconstruction performance in the frequency domain filter performance the reconstruction performance of a filter is based on its ability to remove the high band spectral artifacts (that result from the sampling process) without distorting the valid signal spectral contents within the passband. for video signals, the effect of these artifacts is a variation of the amplitude of small detail elements in the picture (such as highlights or fine pattern details) as the elements move relative to the sampling clock. the result is similar to the aliasing problem and causes a winking of details as they move in the picture. figure 6 shows the problem in the frequency domain. curve a shows the amplitude response of the ML6421 filter, while curve b shows the signal spectrum as it is distorted by the sampling process. curve c shows the composite of the two curves which is the result of passing the sampled waveform through the ML6421 filter. it is clear that the distortion artifacts are reduced significantly. ultimately it is the time domain signal that is viewed on a tv monitor, so the effect of the reconstruction filter on the time domain signal is important. figure 7 shows the sampling artifacts in the time domain. curve a is the original signal, curve b. is the result of ccir601 sampling, and curve c. is the same signal filtered through the ML6421. again the distortions in the signal are essentially removed by the filter. in an effort to measure the time domain effectiveness of a reconstruction filter, figure 8 was generated from a swept frequency waveform. curves a, b, and c are generated as in figure 7, but additional curves d and e help quantify the effect of filtering in the time domain. curve d and curve e represent the envelopes (instantaneous amplitudes) of curves b and c. again it is evident in curve d that the envelope varies significantly due to the sampling process. in curve e, filtering with the ML6421 removes these artifacts and generates an analog output signal that rivals the oversampled (and more ideal) signal waveforms. the ML6421 reduces the amplitude variation from over 6% to less than 1%. figure 5b. typical ML6421 reconstruction application < ideal sinc(x) response < C3db reference marker < a. ML6421 amplitude response < b. signal distortion spectrum < c. reconstructed signal spectrum +10 0 C10 C20 C30 C40 C50 C60 0 5mhz 10mhz 15mhz 20mhz 25mhz frequency r 8 digital inputs red dac (current sourcing g 8 green dac (current sourcing b r analog outputs g b 8 blue dac (current sourcing ML6421 dac load adjusted for 2v p-p 75 w 75 w 75 w +5v
ML6421 11 figure 7. ML6421 reconstruction performance in the time domain figure 8. amplitude ripple of reconstructed swept pulses a. oversampled waveforms b. ccir601 sampled waveforms c. ML6421 reconstructed waveforms a. oversampled signal b. ccir601 sampled signal c. ML6421 filtered signal d. ccir601 sampled waveform e. ML6421 filtered waveform >6% <1%
ML6421 12 ordering information part number bw (mhz) gain temperature range package ML6421cs-1 5.5/5.5/5.5 1x 0c to 70c 16-pin soic wide (s16w) ML6421cs-2 5.5/1.8/1.8 1x 0c to 70c 16-pin soic wide (s16w) ML6421cs-3 8.0/8.0/8.0 1x 0c to 70c 16-pin soic wide (s16w) ML6421cs-4 8.0/3.0/3.0 1x 0c to 70c 16-pin soic wide (s16w) ML6421cs-5 5.5/5.5/5.5 2x 0c to 70c 16-pin soic wide (s16w) ML6421cs-6 5.5/2.5/2.5 2x 0c to 70c 16-pin soic wide (s16w) ML6421cs-7 9.3/9.3/9.3 2x 0c to 70c 16-pin soic wide (s16w) ML6421cs-8 9.3/3.0/3.0 2x 0c to 70c 16-pin soic wide (s16w) seating plane 0.291 - 0.301 (7.39 - 7.65) pin 1 id 0.398 - 0.412 (10.11 - 10.47) 0.400 - 0.414 (10.16 - 10.52) 0.012 - 0.020 (0.30 - 0.51) 0.050 bsc (1.27 bsc) 0.022 - 0.042 (0.56 - 1.07) 0.095 - 0.107 (2.41 - 2.72) 0.005 - 0.013 (0.13 - 0.33) 0.090 - 0.094 (2.28 - 2.39) 16 0.009 - 0.013 (0.22 - 0.33) 0o - 8o 1 0.024 - 0.034 (0.61 - 0.86) (4 places) package: s16w 16-pin wide soic physical dimensions inches (millimeters) micro linear reserves the right to make changes to any product herein to improve reliability, function or design. micro linear does not assume any liability arising out of the application or use of any product described herein, neither does it convey any license under its patent right nor the rights of others. the circuits contained in this data sheet are offered as possible applications only. micro linear makes no warranties or representations as to whether the illustrated circuits infringe any intellectual property rights of others, and will accept no responsibility or liability for use of any application herein. the customer is urged to consult with appropriate legal counsel before deciding on a particular application. 04/01/97 printed in u.s.a. 2092 concourse drive san jose, ca 95131 tel: 408/433-5200 fax: 408/432-0295 ? micro linear 1997 is a registered trademark of micro linear corporation products described in this document may be covered by one or more of the following patents, u.s.: 4,897,611; 4,964,026; 5,027,1 16; 5,281,862; 5,283,483; 5,418,502; 5,508,570; 5,510,727; 5,523,940; 5,546,017; 5,559,470; 5,565,761; 5,592,128; 5,594,376; japan: 2598946; 2619299. other patents are pending.

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