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September 1999
ML6421* Triple Phase and Sinx/x Equalized, Low-Pass Video Filter
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, or 3.0MHz. Each channel incorporates a 6th-order lowpass filter, a first order all-pass filter, a gain boost circuit, and a 75 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 1VP-P over 75 (0.5V to 1.5V), or 2VP-P over 150 (0.5V to 2.5V) with the internal coax drivers.
FEATURES
s s s s s s
5.5, 8.0, 9.3, or 3.0MHz bandwidth 1x or 2x gain 6th-order filter with phase and amplitude equalizer >40dB stopband rejection No external components or clocks 10% frequency accuracy over maximum supply and temperature variation <2% differential gain <2 differential phase <25ns group delay variation Drives 1VP-P into 75, or 2VP-P into 150 5V 10% operation *Some Packages Are Obsolete
s s s s
BLOCK DIAGRAM
VCCB 8
VCCC 6
VCC 5
VCCA 11
VINA 15 3k
BUF
LOW PASS FILTER A
ALL PASS FILTER
SINX/X EQUALIZER
1X/2X BUF
10 VOUTA 3.33k
IBIAS 1k
VINB 16 3k
BUF
LOW PASS FILTER B
ALL PASS FILTER
SINX/X EQUALIZER
1X/2X BUF 3.33k
9
VOUTB
IBIAS 1k
VINC 2 3k RANGE 14 1k
BUF
LOW PASS FILTER C
ALL PASS FILTER
SINX/X EQUALIZER
1X/2X BUF
7 3.33k
VOUTC
IBIAS
12 GND
13 GNDA
4 GNDC
1 GNDB
3 GND
FilterA Filter B Filter C
ML6221-1 5.5MHz 5.5MHz 5.5MHz
1x GAIN ML6421-3 8.0MHz 8.0MHz 8.0MHz
ML6421-4 8.0MHz 3.0MHz 3.0MHz
2x GAIN ML6421-5 ML6421-7 5.5MHz 9.3MHz 5.5MHz 9.3MHz 5.5MHz 9.3MHz
Triple Input/Anti-aliasing Video Filter
1
ML6421
PIN CONFIGURATION
ML6421 16-Pin Wide SOIC (S16W)
GNDB VINC GND GNDC VCC VCCC VOUTC VCCB 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VINB VINB RANGE GNDA GND VCCA VOUTA VOUTA
TOP VIEW
PIN DESCRIPTION
PIN NAME FUNCTION PIN NAME FUNCTION
1 2 3 4 5 6 7
GNDB VINC GND GNDC VCC VCCC VOUTC
Ground pin for filter B. Signal input to filter C. Input impedance is 4k. Power and logic ground.
11 12 13 14
VCC A GND GNDA RANGE
Power supply for filter A. Power and logic ground. Ground pin for filter A. 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 -7; 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. Signal input to filter A. Input impedance is 4k. Signal input to filter B. Input impedance is 4k.
Ground pin for filter C. Positive supply. Power supply for filter C. Output of filter C. Drive is 1VP-P into 75 (0.5V to 1.5V), or 2VP-P into 150 (0.5V to 2.5V). Power supply for filter B: 4.5V to 5.5V. Output of filter B. Drive is 1VP-P into 75 (0.5V to 1.5V), or 2VP-P into 150 (0.5V to 2.5V). Output of filter A. Drive is 1VP-P into 75 (0.5V to 1.5V), or 2VP-P into 150 (0.5V to 2.5V). 15 16 VINA VINB
8 9
VCCB VOUTB
10
VOUTA
2
ML6421
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 (VCC) ....................... -5.5MHz0.3 to +7V GND .................................................. -0.3 to VCC +0.3V Logic Inputs ........................................ -0.3 to VCC +0.3V Input Current per Pin ............................................ 25mA Storage Temperature .................................. -65 to 150C Package Dissipation at TA = 25C .............................. 1W Lead Temperature (Soldering 10 sec) ...................... 260C Thermal Resistance (JA) ..................................... 65C/W
OPERATING CONDITIONS
TSupply Voltage ............................................... 5V 10% Temperature Range ................................ 0C < to < 70C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified VCC = 5V 10% and TA = TMIN to TMAX, RL =75 or 150, VOUT = 2VP-P for 150 Load and VOUT = 1VP-P for 75 Load (Note 1)
SYMBOL GENERAL RIN DR/RIN IBIAS Input Impedance Input R Matching Input Current VIN = 0.5V, range = low VIN = 0.0V, range = high Small Signal Gain VIN = 100mVP-P at 100kHz Differential Gain VIN = 1.1V to 2.5V at 3.58 & 4.43 MHz VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz Differential Phase VIN = 1.1V to 2.5V at 3.58 & 4.43 MHz VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz V IN Input Range Range = 0 ML6421(-1 to -4) ML6421(-5 to -7) Range = 1 ML6421(-5 to -8) Peak Overshoot Crosstalk Rejection 2T, 0.7VP-P pulse fIN = 3.58, fIN = 4.43MHz (Note 6) Channel to Channel Group Delay Matching (fC = 5.5MHz) Channel to Channel Group Matching fIN = 100kHz ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to -4) 0.5 0.5 0.0 0.0 2.0 50 45 10 2.5 V 1.5 2.0 1 % dB dB ns V V V ML6421(-5 to -7) 1 deg ML6421(-1 to -4) 1 deg ML6421(-5 to -7) 1 % ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to -4) -0.5 5.5 -80 45 -125 -210 0 6 1 0.5 6.5 3 4 5 2 k % A A A A dB dB % PARAMETER CONDITIONS MIN TYP MAX UNITS
fIN = 100kHz
2
%
3
ML6421
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER GENERAL (Continued) Output Current CL Load Capacitance Composite Chroma /Luma delay fC = 8.0MHz/9.3MHz 5.50MHZ FILTER (ML6421-1, -5) Bandwidth (monotonic passband) Subcarrier Frequency Gain ML6421-1 fIN = 4.43MHz -0.75dB (Note 5) -0.55dB (Note 5) fIN = 3.58MHz ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to -4) ML6421(-5 to -7) ML6421(-1 to - 4) ML6421(-5 to -7) Attenuation fIN = 10MHz ML6421(-1 to -4) ML6421(-5 to -7) fIN = 50MHz Output Noise Group Delay 8.0MHZ FILTER Bandwidth (monotonic passband) Subcarrier Frequency Gain ML6421-3 or ML6421 4/ML6421-7 Attenuation -3dB (Note 5) fIN = 3.58MHz fIN = 4.43MHz fIN = 17MHz fIN = 85MHz Output Noise Group Delay 9.3MHZ FILTER Bandwidth (monotonic passband) Subcarrier Frequency Gain ML6421-3 or ML6421 4/ML6421-7 Attenuation -2dB (Note 5) fIN = 3.58MHz fIN = 4.43MHz fIN = 17MHz fIN = 85MHz Output Noise Group Delay BW = 30MHz (Note 6) 120 8.4 -0.01 -0.1 20 40 9.3 0.4 0.6 25 42 1000 10.2 0.9 1.1 MHz dB dB dB dB V RMS ns BW = 30MHz (Note 6) 120 7.2 -0.25 -0.11 20 40 8 0.25 0.39 25 42 1000 8.8 0.75 0.89 MHz dB dB dB dB V RMS ns BW = 30MHz (Note 6) 145 4.95 4.95 -0.3 -0.9 - 0.35 1.1 16 20 40 5.50 5.50 0.2 1.4 0.1 1.6 18 25 45 1000 6.05 6.05 0.7 1.9 0.65 2.1 MHz MHz dB dB dB dB dB dB dB V RMS ns fC = 5.5MHz ML6421(-1 to -4) ML6421(-5 to -7) 15 15 8 RL = 0 (short circuit) 175 35 mA pF ns ns ns
(Continued)
CONDITIONS MIN TYP MAX UNITS
4
ML6421
ELECTRICAL CHARACTERISTICS
SYMBOL 3.0MHZ FILTER Bandwidth (monotonic passband) Attenuation -2.5dB (Note 5) fIN = 9.82MHz fIN = 60MHz Output Noise Bandwidth (monotonic passband) Attenuation fIN = 60MHz Output Noise DIGITAL AND DC VIL V IH IIL IIH ICC Logic Input Low Logic Input High Logic Input Low Logic Input High Supply Current RL = 75 Range Range VIN = GND VIN = VCC VIN = 0.5V (Note 4) VIN = 1.5V 110 140 VCC - 0.8 -1 1 135 175 0.8 V V A A mA mA BW = 30MHz (Note 6) BW = 30MHz (Note 6) -2dB (Note 5) fIN = 9.82MHz 3 30 43 3.3 33 50 700 2.7 30 43 3 33 50 700 3.6 3.3 MHz dB dB V RMS MHz dB dB V RMS PARAMETER
(CONTINUED)
CONDITIONS MIN TYP MAX UNITS
Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. Note 2: Maximum resistance on the outputs is 500 in order to improve step response. Note 3: Connect all ground pins to the ground plane via the shortest path. Note 4: Power dissipation: PD = (ICC x VCC) - [3(VOUT2/RL)] Note 5: The bandwidth is the -3dB frequency of the unboosted filter. This represents the attenuation that results from boosting the gain from the -3dB point at the specified frequency. Note 6: These parameters are guaranteed by characterization only.
5
ML6421
10 0 -10 -20
10 0 -10 -20
AMPLITUDE (dB)
-30 -40 -50 -60 -70 -80 -90 100K 1M 10M FREQUENCY (Hz) 100M
AMPLITUDE (dB)
-30
-30 -30 -40 -50 -60 -70 -80 -90 100K 1M 10M FREQUENCY (Hz) 100M
Figure 1. Stop-Band Amplitude vs Frequency (fC = 5.5MHz).
10 0 -10 -20
Figure 2. Stop-Band Amplitude vs Frequency (fC = 8.0MHz).
2 1 0 ML6420-5 ML6421-5
AMPLITUDE (dB)
-30 -30 -40 -50 -60 -70 -80 -90 100K 1M 10M FREQUENCY (Hz) 100M
RELATIVE AMPLITUDE (dB)
-1 -2 -3 -4 -5 -6 -7 -8 100K
1M FREQUENCY (Hz)
10M
Figure 3. Stop-Band Amplitude vs Frequency (fC = 3.0MHz).
Figure 4. Pass-Band Amplitude vs Frequency (fC = 5.5MHz).
6
ML6421
2 1 0 ML6420-7 ML6421-7
220 210 ML6421-5 200
GROUP DELAY (ns)
RELATIVE AMPLITUDE (dB)
-1 -2 -3 -4 -5 -6 -7 -8 100K
190 180 170 160 150 140
ML6421-1 2 3 4 5 6 7
1M FREQUENCY (Hz)
10M
FREQUENCY (MHz)
Figure 5. Pass-Band Amplitude vs Frequency (fC = 9.3MHz).
140 ML6421-7 130 ML6421-3 120
Figure 6. Group Delay vs Frequency (fC = 5.5MHz).
232 222 212 202
GROUP DELAY (ns)
GROUP DELAY (ns)
192 182 172 162
110
100
152 142
90
1
2
3
4
5
6
7
8
9
10
11
132 100K
FREQUENCY (mHz)
3.5MHz FREQUENCY (Hz)
7MHz
Figure 7. Group Delay vs Frequency (fC = 8.0MHz).
Figure 8. Group Delay vs Frequency (fC = 3.0MHz).
7
ML6421
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 75 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 75 to ground.
APPLICATION GUIDELINES
OUTPUT CONSIDERATIONS The triple filters have unity gain. The circuit has unity gain (0dB) when connected to a 150 load, and a -6dB gain when driving a 75 load via a 75 series output resistor. The output may be either AC or DC coupled. For AC coupling, the -3dB point should be 5Hz or less. There must also be a DC path of -500 to ground for output biasing. INPUT CONSIDERATIONS The input resistance is 4k. 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 75 or 150 resistor to ground may need to be added to the DAC output (filter input).
+5V 0.001F 0.1F 100F FB2 SUPPLY NOISE CLAMPING 47 3.1k 1F INPUT DECOUPLING 0.1F INC INPUT SIGNAL = 2VP-P 85 INPUT TERMINATION FB1 0.1F 1nF 4 GNDC 5 VCC 1nF 6 VCCC OUTC 75 1nF 8 VCCB 0.1F VOUTB 0.1F 7 VOUTC VOUTA 9 75 VCCA 10 75 OUTB OUTA GND 11 0.1F GNDA 12 1nF 100F 85 100F DC BIAS 1k 3 GND RANGE 0.1F 13 INA 14 1k 1 GNDB 3.1k 2 VINC VINA 15 VINB 1k 16 100F 3.1k 1F 0.1F INB 85 1F 47
47
Figure 9. ML6421 AC Coupled DC Bias Test Circuit
8
ML6421
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 VCC, VCCC, VCCB and VCCA for maximum noise rejection (Figure 9). 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: PD = ICC x VCC -
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, the ML6421-4 with the 8.0, and two 3.0MHz filters are most appropriate. 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. 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
1
6 V RL !
OUT
2
x3
"# $#
(1)
This is a measure of the amount of current the part sinks (current in - current out to the load). Under worst case conditions: PD = 0.175 x 5.5 - . 5 15 x 3 "# = 872.5mW 75 ! $#
2
0
4 THEORETICAL SINX/X CORRECTION FOR 13.5MHz SAMPLING 2 DIGITAL INPUTS R 8 RED DAC (CURRENT SOURCING +5V ML6421 75 ANALOG OUTPUTS R
AMPLITUDE
G 0 B -2 SINX/X ERROR FOR TYPICAL DAC AT 13.5MHz
8
GREEN DAC (CURRENT SOURCING
G 75
8
BLUE DAC (CURRENT SOURCING DAC LOAD ADJUSTED FOR 2VP-P
B 75
-4 0 1 2 3 4 5 FREQUENCY (MHz) 6 7
Figure 10. Sinx/x Frequency Response
Figure 11. Typical ML6421 Reconstruction Application
9
ML6421
ML6421 VIDEO LOW PASS FILTER
(CONTINUIED 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 13 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 14 was generated from a swept frequency waveform. Curves A, B, and C are generated as in Figure 13, 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%. 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 75 or 150). Resistance values should be adjusted to provide 2VP-P at the input of the ML6421. The ML6421 will drive 75 source termination resistors (making the total load 150) so that no external drivers or amplifiers are required.
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 12 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
Figure 12. ML6421 Reconstruction Performance in the Frequency Domain
10
ML6421
Figure 13. ML6421 Reconstruction Performance in the Time Domain
Figure 14. Amplitude Ripple of Reconstructed Swept Pulses
11
ML6421
PHYSICAL DIMENSIONS
Package: S16W 16-Pin Wide SOIC
0.400 - 0.414 (10.16 - 10.52) 16
0.291 - 0.301 0.398 - 0.412 (7.39 - 7.65) (10.11 - 10.47) PIN 1 ID
1 0.024 - 0.034 (0.61 - 0.86) (4 PLACES) 0.050 BSC (1.27 BSC) 0.095 - 0.107 (2.41 - 2.72) 0 - 8
0.090 - 0.094 (2.28 - 2.39)
0.012 - 0.020 (0.30 - 0.51)
SEATING PLANE
0.005 - 0.013 (0.13 - 0.33)
0.022 - 0.042 (0.56 - 1.07)
0.009 - 0.013 (0.22 - 0.33)
12
ML6421
ORDERING INFORMATION
PART NUMBER ML6421CS-1 ML6421CS-3 ML6421CS-4 ML6421CS-5 ML6421CS-7 BW (MHZ) 5.5/5.5/5.5 8.0/8.0/8.0 8.0/3.0/3.0 5.5/5.5/2.5 9.3/9.3/9.3 GAIN 1X 1X 1X 2X 2X TEMPERATURE RANGE 0C to 70C 0C to 70C 0C to 70C 0C to 70C 0C to 70C PACKAGE 16-pin SOIC wide (S16W) 16-pin SOIC wide (S16W) 16-pin SOIC wide (S16W)(OBS) 16-pin SOIC wide (S16W) 16-pin SOIC wide (S16W)
Micro Linear Corporation 2092 Concourse Drive San Jose, CA 95131 Tel: (408) 433-5200 Fax: (408) 432-0295 www.microlinear.com
(c) Micro Linear 1999. property of their respective owners.
is a registered trademark of Micro Linear Corporation. All other trademarks are the
Products described herein may be covered by one or more of the following U.S. patents: 4,897,611; 4,964,026; 5,027,116; 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; 5,652,479; 5,661,427; 5,663,874; 5,672,959; 5,689,167; 5,714,897; 5,717,798; 5,742,151; 5,747,977; 5,754,012; 5,757,174; 5,767,653; 5,777,514; 5,793,168; 5,798,635; 5,804,950; 5,808,455; 5,811,999; 5,818,207; 5,818,669; 5,825,165; 5,825,223; 5,838,723; 5.844,378; 5,844,941. Japan: 2,598,946; 2,619,299; 2,704,176; 2,821,714. Other patents are pending. Micro Linear makes no representations or warranties with respect to the accuracy, utility, or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. No license, express or implied, by estoppel or otherwise, to any patents or other intellectual property rights is granted by this document. The circuits contained in this document are offered as possible applications only. Particular uses or applications may invalidate some of the specifications and/or product descriptions contained herein. The customer is urged to perform its own engineering review before deciding on a particular application. Micro Linear assumes no liability whatsoever, and disclaims any express or implied warranty, relating to sale and/or use of Micro Linear products including liability or warranties relating to merchantability, fitness for a particular purpose, or infringement of any intellectual property right. Micro Linear products are not designed for use in medical, life saving, or life sustaining applications.
DS6421-01
13

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