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June 1999 PRELIMINARY
ML6423* Dual S-Video Lowpass Filter with Phase and Sinx/x Equalization
GENERAL DESCRIPTION
The ML6423 monolithic BiCMOS 6th-order filter provides a two-channel fixed frequency lowpass filtering for video applications. This dual phase equalized filter with sinx/x correction is designed for reconstruction filtering at the output of a Video DAC. A composite sum output eliminates the need for a third DAC. Cutoff frequencies are either 5.5MHz or 9.6MHz. Each channel incorporates a 6th-order lowpass filter, a first order allpass filter, a gain boost circuit, and a 75W 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 2X gain filters are powered from a single 5V supply, and can drive 1VP-P into 75W (0.5V to 1.5V), or 2VP-P into 150W (0.5V to 2.5V) with the internal coax drivers.
FEATURES
s 5.5 or 9.6MHz bandwidth with 6dB gain s >40dB stopband rejection s No external components or clocks s 10% frequency accuracy over maximum supply and temperature variation s <2% differential gain, <2 differential phase s <20ns group delay variation s 5V 10% operation s Composite (sum) output s High sink current for AC coupled loads, ML6423-5 * This Product Is End Of Life As Of August 1, 2000
BLOCK DIAGRAM
10 VCCB 7 VCCC 4 VCC 13 VCCA
VINA (Y) 16 2k IBIAS 2k BUF
VOUTA (Y) LOWPASS FILTER A ALLPASS FILTER SINX/X EQUALIZER 2X BUF 3.43k 12
15 RANGE
2X BUF
VOUTB (CV) 8 3.43k
VINC (C) 1 2k IBIAS 2k GND 2 BUF
LOWPASS FILTER C
ALLPASS FILTER
SINX/X EQUALIZER
2X BUF
VOUTC (C) 6 3.43k
GNDA 14
GNDC 3
GNDB 9
Filter A Filter C
ML6423-1 5.50MHz 5.50MHz
ML6423-2 9.6MHz 9.6MHz
ML6423-5 9.6MHz 9.6MHz
1
ML6423
PIN CONFIGURATION
ML6423 16-Pin Wide SOIC (S16W)
VINC GND GNDC VCC NC VOUTC VCCC VOUTB
1 2 3 4 5 6 7 8 TOP VIEW
16 15 14 13 12 11 10 9
VINA RANGE GNDA VCCA VOUTA NC VCCB GNDB
PIN DESCRIPTION
PIN NAME FUNCTION PIN NAME FUNCTION
1 2 3 4 5 6
VINC GND GNDC VCC NC VOUTC
Signal input to filter C. Input impedance is 4kW. Power and logic ground.
10 11 12
VCCB NC VOUTA
Power supply voltage for output B. No Connect Output of filter A. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). Power supply voltage for filter A. Ground pin for filter A. Input signal range select. 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, while the output range is 0.5V to 2.5V. Signal input to filter A. Input impedance is 4kW.
Ground pin for filter C. Positive supply: 4.5V to 5.5V. 13 No Connect 14 Output of filter C. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). Power supply voltage for filter C. Sum of Filter A and Filter C. Drive is 1VP-P into 75W (0.5V to 1.5V) or 2VP-P into 150W (0.5V to 2.5V). 16 Ground pin for output B. 15
VCCA GNDA RANGE
7 8
VCCC VOUTB
9
GNDB
VINA
2
ML6423
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) ...................................... -0.3 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 Lead Temperature (Soldering 10 sec) ..................... 150C Thermal Resistance (qJA) ..................................... 65C/W
OPERATING CONDITIONS
Supply Voltage ................................................. 5V 10% Temperature Range ...................................... 0C to 70C
ELECTRICAL CHARACTERISTICS
Unless otherwise specified VCC = 5V 10%, RL =75W or 150W, VOUT = 2VP-P for 150W Load and VOUT = 1VP-P for 75W Load, TA = Operating Temperature Range (Notes 1, 2, 3)
SYMBOL GENERAL RIN DR/RIN IBIAS Input Impedance Input R Matching Input Current VIN = 0.5V, RANGE = low VIN = 0.0V, RANGE = high Differential Gain Differential Phase V IN Input Range VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz VIN = 0.8V to 1.5V at 3.58 & 4.43 MHz RANGE = Low RANGE = High Peak Overshoot Crosstalk Rejection Channel to Channel Group Delay Matching (fC = 5.5MHz) Channel to Channel Gain Matching Output Current CL Load Capacitance Composite Chroma/Luma delay fC = 5.5MHz fC = 9.6MHz 5.50MHZ FILTER Bandwidth (monotonic passband) Subcarrier Frequency Gain ML6423-1 Attenuation -0.55dB (Note 4) fIN = 3.58MHz fIN = 4.43MHz fIN = 10MHz fIN = 50MHz Output Noise Group Delay BW = 30MHz 180 4.95 0.9 1.1 20 45 5.50 1.4 1.6 25 55 1 6.05 2.3 2.5 MHz dB dB dB dB mVRMS ns 15 8 2T, 0.7VP-P pulse fIN = 3.58, fIN = 4.43MHz fIN = 100kHz 45 3 0.5 0.0 2.0 -210 1 1 1.5 1.0 45 A % deg V V % dB ns 3k 4 5 2 kW % A PARAMETER CONDITIONS MIN TYP MAX UNITS
fIN = 100kHz RL = 0 (short circuit)
1.5 75 35
% mA pF ns ns
3
ML6423
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER 5.50MHZ FILTER (Continued) Small Signal Gain Composite (CV) Small Signal Gain 9.6MHZ FILTER Bandwidth (monotonic passband) Subcarrier Frequency Gain ML6423-2 Subcarrier Frequncy Gain ML6423-5 Attenuation -2dB (Note 4) fIN = 3.58MHz fIN = 4.43MHz fIN = 3.58MHz fIN = 4.43MHz fIN = 17MHz fIN = 85MHz Output Noise Group Delay Composite (CV) Small Signal Gain I CC ML6423-5 Supply Current RL = 150W VINA, C = 100mVP-P at 100kHz VIN = 0.5V (Note 5) VIN = 1.5V ML6423-5 VOUTA, VOUTB sink current ML6423-5 VOUTC sink current ML6423-5 Output DC Level DIGITAL AND DC VIL VIH IIL IIL ICC Logic Input Low Logic Input High Logic Input Low Logic Input High Supply Current RL = 150W Range Range VIN = GND VIN = VCC VIN = 0.5V (Note 5) VIN = 1.5V
Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions. Note 2: Maximum resistance on the outputs is 500W in order to improve step response. Note 3: Connect all ground pins to the ground plane via the shortest path. Note 4: 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 5: Power dissipation: PD = (ICC VCC) - [3(VOUT2/RL)]
(Continued)
CONDITIONS MIN TYP MAX UNITS
VIN = 100mVP-P at 100kHz, Filter A or C VINA, C = 100mVP-P at 100kHz
5.5 11
6 12
6.5 13
dB dB
8.6 -0.1 -0.1 -0.1 -0.1 20 45
9.6 0.4 0.6 0.4 0.6 25 55
10.6 1.1 1.3 1.9 1.1
MHz dB dB dB dB dB dB
BW = 30MHz
1 100 11 12 140 170 8.3 4.3 11.5 6.5 0.5 13 175 215
mVRMS ns dB mA mA mA mA V
VIN = 0.5V VIN = 0.5V VIN = 0.5V, Range = Low
0.8 VCC - 0.8 -1 1 110 140 135 175
V V A A mA mA
4
ML6423
16 6 -4 -14
AMPLITUDE (dB)
16 6 -4 -14
-24 -34 -44 -54 -64 -74 -84 100K
AMPLITUDE (dB)
1M 10M FREQUENCY (Hz) 100M
-24 -34 -44 -54 -64 -74 -84 100K
1M 10M FREQUENCY (Hz)
100M
Figure 1a. Stop-Band Amplitude vs. Frequency (fC = 5.5MHz)
7.5 7.0 6.5 ML6423-1 6.0
AMPLITUDE (dB)
Figure 1b. Stop-Band Amplitude vs. Frequency (fC = 9.6MHz)
7.5 7.0 6.5 6.0 ML6423-2
5.5 5.0 4.5 4.0 3.5 3.0 2.5 100K
AMPLITUDE (dB)
ML6422-2 5.5 5.0 4.5 4.0 3.5 3.0 2.5 100K
1M FREQUENCY (Hz)
5.5MHz 10M
1M FREQUENCY (Hz)
5.5MHz 10M
Figure 2a. Pass-Band Amplitude vs. Frequency (fC = 5.5MHz)
220 200 180 160
GROUP DELAY (ns)
Figure 2b. Pass-Band Amplitude vs. Frequency (fC = 9.6MHz)
130 125 120 115 GROUP DELAY (ns) 110 105 100 95 90 85 80 100K
140 120 100 80 60 40 20 100K
5.5MHz FREQUENCY (Hz)
10MHz
5M FREQUENCY (Hz)
9.3M 10M
Figure 3a. Group Delay vs. Frequency (fC = 5.5MHz)
Figure 3b. Group Delay vs. Frequency (fC = 9.6MHz)
5
ML6423
FUNCTIONAL DESCRIPTION
The ML6423 single-chip dual video filter is intended for low cost professional and consumer video applications. Each of the two channels incorporates an input buffer amplifier, a 6th-order lowpass filter, a 1st-order allpass equalizer, sinx/x equalizer and an output 2X gain amplifier capable of driving 75W to ground. A third output (B) is the sum of the A and C inputs and have the identical output amplifier as the A and C channels. The ML6423 can be driven by a DAC with RANGE down to 0V. When RANGE is low the input range is 0.5V to 1.5V. When the input signal range is 0V to 0.1V, 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 75W to ground.
APPLICATION GUIDELINES
OUTPUT & INPUT CONSIDERATIONS The dual filters have 2X gain. The circuit has 2X gain (6dB) when connected to a 150W load, and 0dB gain when driving a 75W load via a 75W 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 500W to ground for output biasing. The ML6423-5 provides higher sink current to better drive AC coupled loads. The input resistance is 4kW. The input may be either DC or AC coupled. (Note that each input sources 80 to 125A of bias current). The ML6423 is designed to be directly driven by a DAC. For current output video DACs, a 75W or 150W resistor to ground may need to be added to the DAC output (filter input).
+5V + 0.1F 1nF 100F FB2
SUPPLY NOISE CLAMPING
100
100
INPUT DECOUPLING 0.1F VINC INPUT SIGNAL = 1VP-P 85 + 100F
1F
2.56k
1F
100F + 85
VINA
2.56k 1 DC BIAS 1k 2 GND RANGE 15 VINC VINA 16 1k
0.1F
INPUT TERMINATION RESISTOR FB1 0.1F
1nF 3
GNDC
GNDA
14 0.1F
4
VCC
VCCA
13
1nF
5 VOUTC 75 0.1F 7 VOUTB 75 1nF
NC
VOUTA
12 75 11
VOUTA
6
VOUTC
NC
VCCC
VCCB
10 0.1F
8
VOUTB
GNDB
9
1nF
Figure 4. ML6423 AC Coupled DC Bias Test Circuit
6
ML6423
APPLICATION GUIDELINES (Continued)
LAYOUT CONSIDERATIONS In order to obtain full performance from these dual 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 all VCC pins 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 two filters and a sum output driver in one package, space the signal leads away from each other as much as possible. POWER CONSIDERATIONS The ML6423 power dissipation follows the formula: In a typical application (Figure 5b) the ML6423 is used as the final output device in a video processing chain. In this case, inputs to the ML6423 are supplied by DAC outputs with their associated load resistors (typically 75W or 150W). Resistance values should be adjusted to provide 1VP-P at the input of the ML6423. The ML6423 will drive 75W source termination resistors (making the total load 150W) so that no external drivers or amplifiers are required. Composite: When one or more composite signals need to be filtered, then the 5.5MHz and 9.6MHz filters permit filtering of one, two, or three composite signals. Over Sampling: While the ML6423 filters can eliminate the need for over sampling combined with digital filtering, there are times when over sampling is used. For these situations, 9.3MHz could be used in place of 5.5MHz. NTSC/PAL: A 5.5MHz cutoff 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 (Figure 5a). The ML6423 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.
PD = (ICC VCC ) -
V ! RL
OUT
2
3
"# #$
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 5.5) FILTER SELECTION The ML6423 provides several choices in filter cutoff frequencies depending on the application. S-Video: For Y/C (S-video) and Y/C + CV (Composite Video) systems the 5.5MHz or 9.6MHz 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 lowpass 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.
15 3 "# = 8725mW . 75 $# . !
2
4 THEORETICAL SINX/X CORRECTION FOR 13.5MHz SAMPLING 2
AMPLITUDE
0
-2 SINX/X ERROR FOR TYPICAL DAC AT 13.5MHz
-4 0 1 2 3 4 5 FREQUENCY (MHz) 6 7
Figure 5a. Sinx/x Frequency Response
7
ML6423
10 IDEAL SINX/X RESPONSE 0 -3dB REFERENCE MARKER
-10
AMPLITUDE (dB)
A. ML6423 AMPLITUDE RESPONSE
-20 B. SIGNAL DISTORTION SPECTRUM -30
C. RECONSTRUCTED SIGNAL SPECTRUM
-40
-50
-60 0 5 10 15 20 25 FREQUENCY (MHz)
Figure 6. ML6423 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 ML6423 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 ML6423. 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 ML6423. 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. Curves D and 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 ML6423 removes these artifacts and generates an analog output signal that rivals the oversampled (and more ideal) signal waveforms. The ML6423 reduces the amplitude variation from over 6% to less than 1%.
DAC INPUTS Y DAC (CURRENT SOURCING
+5V ML6423 75
ANALOG OUTPUTS Y
+
C DAC (CURRENT SOURCING DAC LOAD ADJUSTED FOR 1VP-P
CV 75
C 75
Figure 5b. Typical ML6423 Reconstruction Application
8
ML6423
A. OVERSAMPLED WAVEFORMS
B. CCIR601 SAMPLED WAVEFORMS
C. ML6423 RECONSTRUCTED WAVEFORMS
Figure 7. ML6423 Reconstruction Performance in the Time Domain
A. OVERSAMPLED SIGNAL
B. CCIR601 SAMPLED SIGNAL
C. ML6423 FILTERED SIGNAL
D. CCIR601 SAMPLED WAVEFORM >6% E. ML6423 FILTERED WAVEFORM
<1%
Figure 8. Amplitude Ripple of Reconstructed Swept Pulses
9
ML6423
PHYSICAL DIMENSIONS inches (millimeters)
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)
ORDERING INFORMATION
PART NUMBER ML6423CS-1 (EOL) ML6423CS-2 (EOL) ML6423CS-5 (Obsolete) BW (MHZ) 5.5/5.5 9.6/9.6 9.6/9.6 TEMPERATURE RANGE 0C to 70C 0C to 70C 0C to 70C PACKAGE 16-pin Wide SOIC (S16W) 16-pin Wide SOIC (S16W) 16-pin Wide SOIC (S16W)
(c) Micro Linear 2000. 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. 2092 Concourse Drive San Jose, CA 95131 Tel: 408/433-5200 Fax: 408/432-0295 www.microlinear.com
10
DS6423-01

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