Page 1
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 1V
into 75W (0.5V to 1.5V), or 2V
P-P
P-P
into
150W (0.5V to 2.5V) with the internal coax drivers.
BLOCK DIAGRAM
10
BV
V
CC
7
V
CC
FEATURES
■ 5.5 or 9.6MHz bandwidth with 6dB gain
■ >40dB stopband rejection
■ No external components or clocks
■ ±10% frequency accuracy over maximum supply
and temperature variation
■ <2% differential gain, <2° differential phase
■ <20ns group delay variation
■ 5V ±10% operation
■ Composite (sum) output
■ High sink current for AC coupled loads, ML6423-5
* This Product Is End Of Life As Of August 1, 2000
4
C
CC
13
A
V
CC
16
15
1
VINA (Y)
RANGE
VINC (C)
2kΩ
2kΩ
2kΩ
2kΩ
I
BIAS
BUF
LOWPASS
FILTER A
ALLPASS
FILTER
SINX/X
EQUALIZER
∑
I
BIAS
BUF
LOWPASS
FILTER C
GND
2
GNDA
14
ALLPASS
FILTER
GNDC
ML6423-1 ML6423-2 ML6423-5
Filter A 5.50MHz 9.6MHz 9.6MHz
Filter C 5.50MHz 9.6MHz 9.6MHz
SINX/X
EQUALIZER
GNDB
3
A (Y)
V
3.43kΩ
V
3.43kΩ
3.43kΩ
OUT
OUT
V
OUT
12
B (CV)
8
C (C)
6
2X
BUF
2X
BUF
2X
BUF
9
1
Page 2
ML6423
PIN CONFIGURATION
ML6423
16-Pin Wide SOIC (S16W)
VINC
GND
GNDC
V
CC
NC
V
C
OUT
VCCC
V
B
OUT
PIN DESCRIPTION
PIN NAME FUNCTION
1VINC Signal input to filter C. Input
impedance is 4kW.
2 GND Power and logic ground.
3 GNDC Ground pin for filter C.
4V
CC
5 NC No Connect
6V
C Output of filter C. Drive is 1V
OUT
7VCCC Power supply voltage for filter C.
8V
B Sum of Filter A and Filter C. Drive is
OUT
9 GNDB Ground pin for output B.
Positive supply: 4.5V to 5.5V.
75W (0.5V to 1.5V) or 2V
P-P
(0.5V to 2.5V).
1V
into 75W (0.5V to 1.5V) or 2V
P-P
into 150W (0.5V to 2.5V).
into 150W
P-P
1
2
3
4
5
6
7
8
into
TOP VIEW
P-P
VINA
16
RANGE
15
GNDA
14
VCCA
13
V
A
12
11
10
OUT
NC
VCCB
GNDB
9
PIN NAME FUNCTION
10 VCCB Power supply voltage for output B.
11 NC No Connect
12 V
A Output of filter A. Drive is 1V
OUT
75W (0.5V to 1.5V) or 2V
P-P
into 150W
P-P
into
(0.5V to 2.5V).
13 VCCA Power supply voltage for filter A.
14 GNDA Ground pin for filter A.
15 RANGE 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.
16 VINA Signal input to filter A. Input
impedance is 4kW.
2
Page 3
ABSOLUTE MAXIMUM RATINGS
ML6423
Absolute maximum ratings are those values beyond
which the device could be permanently damaged.
Absolute maximum ratings are stress ratings only and
Storage Temperature .................................. –65° to 150°C
Lead Temperature (Soldering 10 sec) ..................... 150°C
Thermal Resistance (qJA) ..................................... 65°C/W
functional device operation is not implied.
OPERATING CONDITIONS
Supply Voltage (VCC) ...................................... –0.3 to 7V
GND .................................................. –0.3 to VCC +0.3V
Logic Inputs ........................................ –0.3 to VCC +0.3V
Supply Voltage ................................................. 5V ±10%
Temperature Range ...................................... 0°C to 70°C
Input Current per Pin............................................±25mA
ELECTRICAL CHARACTERISTICS
Unless otherwise specified VCC = 5V ± 10%, RL =75W or 150W, V
Load, TA = Operating Temperature Range (Notes 1, 2, 3)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
GENERAL
R
DR/R
I
BIAS
Input Impedance 3k 4 5 kW
IN
Input R Matching ±2 %
IN
Input Current VIN = 0.5V, RANGE = low 45 µA
VIN = 0.0V, RANGE = high –210 µA
Differential Gain VIN = 0.8V to 1.5V
at 3.58 & 4.43 MHz 1 %
OUT
= 2V
for 150W Load and V
P-P
OUT
= 1V
for 75W
P-P
Differential Phase VIN = 0.8V to 1.5V
V
C
5.50MHZ FILTER
Input Range RANGE = Low 0.5 1.5 V
IN
Peak Overshoot 2T, 0.7V
Crosstalk Rejection fIN = 3.58, fIN = 4.43MHz 45 dB
Channel to Channel f
Group Delay Matching
(fC = 5.5MHz)
Channel to Channel f
Gain Matching
Output Current RL = 0 (short circuit) 75 mA
Load Capacitance 35 pF
L
Composite Chroma/Luma delay fC = 5.5MHz ±15 ns
Bandwidth (monotonic passband) –0.55dB (Note 4) 4.95 5.50 6.05 MHz
Subcarrier Frequency Gain fIN = 3.58MHz 0.9 1.4 2.3 dB
ML6423-1 fIN = 4.43MHz 1.1 1.6 2.5 dB
at 3.58 & 4.43 MHz 1 deg
RANGE = High 0.0 1.0 V
pulse 2.0 %
P-P
= 100kHz ±3 ns
IN
= 100kHz ±1.5 %
IN
fC = 9.6MHz ±8 ns
Attenuation fIN = 10MHz 20 25 dB
fIN = 50MHz 45 55 dB
Output Noise BW = 30MHz 1 mV
Group Delay 180 ns
RMS
3
Page 4
ML6423
ELECTRICAL CHARACTERISTICS (Continued)
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
5.50MHZ FILTER (Continued)
Small Signal Gain VIN = 100mV
Composite (CV) Small Signal Gain VINA, C = 100mV
9.6MHZ FILTER
Bandwidth (monotonic passband) –2dB (Note 4) 8.6 9.6 10.6 MHz
Subcarrier Frequency Gain fIN = 3.58MHz –0.1 0.4 1.1 dB
ML6423-2 fIN = 4.43MHz –0.1 0.6 1.3 dB
Subcarrier Frequncy Gain fIN = 3.58MHz –0.1 0.4 1.9 dB
ML6423-5 fIN = 4.43MHz –0.1 0.6 1.1 dB
Attenuation fIN = 17MHz 20 25 dB
Output Noise BW = 30MHz 1 mV
Group Delay 100 ns
Composite (CV) Small Signal Gain VINA, C = 100mV
I
CC
ML6423-5 Supply Current RL = 150W VIN = 0.5V (Note 5) 140 175 mA
ML6423-5 V
ML6423-5 V
ML6423-5 Output DC Level VIN = 0.5V, Range = Low 0.5 V
at 100kHz, 5.5 6 6.5 dB
P-P
Filter A or C
at 100kHz 11 12 13 dB
P-P
fIN = 85MHz 45 55 dB
at 100kHz 11 12 13 dB
P-P
VIN = 1.5V 170 215 mA
A, V
OUT
C sink current VIN = 0.5V 4.3 6.5 mA
OUT
B sink current VIN = 0.5V 8.3 11.5 mA
OUT
RMS
DIGITAL AND DC
V
V
I
I
Logic Input Low Range 0.8 V
IL
Logic Input High Range VCC – 0.8 V
IH
Logic Input Low VIN = GND –1 µA
IL
Logic Input High VIN = V
IL
CC
1µA
ICCSupply Current RL = 150W VIN = 0.5V (Note 5) 110 135 mA
VIN = 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 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
Note 5: Power dissipation: P
boosting the gain from the –3dB point at the specified frequency.
= (ICC ´ VCC) – [3(V
D
OUT
2
/RL)]
4
Page 5
ML6423
16
6
–4
–14
–24
–34
–44
AMPLITUDE (dB)
–54
–64
–74
–84
100K 1M 10M 100M
FREQUENCY (Hz)
Figure 1a. Stop-Band Amplitude vs. Frequency
(fC = 5.5MHz)
7.5
7.0
6.5
6.0
5.5
ML6423-1
16
6
–4
–14
–24
–34
–44
AMPLITUDE (dB)
–54
–64
–74
–84
100K 1M 10M 100M
FREQUENCY (Hz)
Figure 1b. Stop-Band Amplitude vs. Frequency
(fC = 9.6MHz)
7.5
7.0
6.5
6.0
5.5
ML6423-2
ML6422-2
5.0
4.5
AMPLITUDE (dB)
4.0
3.5
3.0
2.5
100K 1M 10M5.5MHz
FREQUENCY (Hz)
Figure 2a. Pass-Band Amplitude vs. Frequency
(fC = 5.5MHz)
220
200
180
160
140
120
100
GROUP DELAY (ns)
80
5.0
4.5
AMPLITUDE (dB)
4.0
3.5
3.0
2.5
100K 1M 10M5.5MHz
FREQUENCY (Hz)
Figure 2b. Pass-Band Amplitude vs. Frequency
(fC = 9.6MHz)
130
125
120
115
110
105
100
GROUP DELAY (ns)
95
60
40
20
100K 5.5MHz 10MHz
FREQUENCY (Hz)
Figure 3a. Group Delay vs. Frequency
(fC = 5.5MHz)
90
85
80
100K 5M 10M
FREQUENCY (Hz)
9.3M
Figure 3b. Group Delay vs. Frequency
(fC = 9.6MHz)
5
Page 6
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.
SUPPLY NOISE
+5V
0.1µF
1nF
+
100µF
FB2
CLAMPING
100Ω
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 125µA
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).
100Ω
V
C
IN
INPUT SIGNAL
= 1V
P-P
C
V
OUT
B
V
OUT
INPUT
DECOUPLING
0.1µF
85Ω
INPUT
TERMINATION
RESISTOR
75Ω
75Ω
+
100µF
FB1
DC
BIAS
2.56kΩ
1kΩ
0.1µF
1µF
1nF
1nF
0.1µF
1
2
3
4
5
6
7
8
V
C
IN
GND
GNDC
V
CC
NC
V
OUT
V
CC
V
OUT
100µF
1µF
2.56kΩ
16
V
A
IN
1k
15
RANGE
0.1µF
14
GNDA
1nF
13
V
A
CC
12
V
A
OUT
11
C
C
B
NC
V
CC
GNDB
10
0.1µF
B
1nF
9
+
85Ω
0.1µF
75Ω
V
OUT
A
V
IN
A
Figure 4. ML6423 AC Coupled DC Bias Test Circuit
6
Page 7
APPLICATION GUIDELINES (Continued)
ML6423
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, 0.1µF 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:
= -
DCC CC
This is a measure of the amount of current the part sinks
(current in – current out to the load).
!
P(I V)
2
V
OUT
RL
"
3
#
#
$
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.
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
1V
at the input of the ML6423. The ML6423 will drive
P-P
75W source termination resistors (making the total load
150W) so that no external drivers or amplifiers are
required.
Under worst case conditions:
4
2
.
PmW
=-
D
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
75
!
"
=(. .)
3 8725
.0175 55
#
#
$
2
0
AMPLITUDE
–2
–4
01234567
THEORETICAL SINX/X
CORRECTION FOR
13.5MHz SAMPLING
SINX/X ERROR FOR
TYPICAL DAC AT 13.5MHz
FREQUENCY (MHz)
Figure 5a. Sinx/x Frequency Response
7
Page 8
ML6423
10
IDEAL SINX/X RESPONSE
0
–3dB REFERENCE MARKER
–10
–20
–30
AMPLITUDE (dB)
–40
–50
–60
0 5 10 15 20 25
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.
DAC
INPUTS
Y
C
DAC
(CURRENT SOURCING
DAC
(CURRENT SOURCING
DAC LOAD
ADJUSTED FOR
1V
P-P
Figure 5b. Typical ML6423 Reconstruction Application
+5V
ML6423
+
75Ω
75Ω
75Ω
ANALOG
OUTPUTS
Y
CV
C
A. ML6423 AMPLITUDE RESPONSE
B. SIGNAL DISTORTION SPECTRUM
C. RECONSTRUCTED SIGNAL
SPECTRUM
FREQUENCY (MHz)
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%.
8
Page 9
A. OVERSAMPLED
WAVEFORMS
B. CCIR601 SAMPLED
WAVEFORMS
C. ML6423
RECONSTRUCTED
WAVEFORMS
ML6423
A. OVERSAMPLED
SIGNAL
B. CCIR601 SAMPLED
SIGNAL
C. ML6423 FILTERED
SIGNAL
D. CCIR601 SAMPLED
WAVEFORM
Figure 7. ML6423 Reconstruction Performance in the Time Domain
>6%
E. ML6423 FILTERED
WAVEFORM
<1%
Figure 8. Amplitude Ripple of Reconstructed Swept Pulses
9
Page 10
ML6423
PHYSICAL DIMENSIONS inches (millimeters)
Package: S16W
16-Pin Wide SOIC
0.400 - 0.414
16
(10.16 - 10.52)
0.024 - 0.034
(0.61 - 0.86)
(4 PLACES)
0.090 - 0.094
(2.28 - 2.39)
1
PIN 1 ID
0.050 BSC
(1.27 BSC)
0.012 - 0.020
(0.30 - 0.51)
0.291 - 0.301
(7.39 - 7.65)
0.095 - 0.107
(2.41 - 2.72)
SEATING PLANE
0.398 - 0.412
(10.11 - 10.47)
0.005 - 0.013
(0.13 - 0.33)
0º - 8º
0.022 - 0.042
(0.56 - 1.07)
ORDERING INFORMATION
PART NUMBER BW (MHZ) TEMPERATURE RANGE PACKAGE
ML6423CS-1 (EOL) 5.5/5.5 0°C to 70°C 16-pin Wide SOIC (S16W)
ML6423CS-2 (EOL) 9.6/9.6 0°C to 70°C 16-pin Wide SOIC (S16W)
ML6423CS-5 (Obsolete) 9.6/9.6 0°C to 70°C 16-pin Wide SOIC (S16W)
0.009 - 0.013
(0.22 - 0.33)
© Micro Linear 2000. is a registered trademark of Micro Linear Corporation. All other trademarks are the
property of their respective owners.
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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