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 75
W 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
P-P
into 75
W (0.5V to 1.5V), or 2V
P-P
into
150
W (0.5V to 2.5V) with the internal coax drivers.
June 1999
PRELIMINARY
ML6423
*
Dual S-Video Lowpass Filter with
Phase and Sinx/x Equalization
1
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
ML6423-1
ML6423-2
ML6423-5
Filter A
5.50MHz
9.6MHz
9.6MHz
Filter C
5.50MHz
9.6MHz
9.6MHz
BLOCK DIAGRAM
16
4
7
V
IN
A (Y)
12
V
OUT
A (Y)
2k
2k
3.43k
9
8
V
OUT
B (CV)
3.43k
1
15
V
IN
C (C)
6
V
OUT
C (C)
3.43k
V
CC
C
10
V
CC
B
V
CC
13
V
CC
A
GNDC
14
GNDA
2
GND
RANGE
GNDB
I
BIAS
I
BIAS
2k
2k
BUF
2X
BUF
LOWPASS
FILTER A
BUF
LOWPASS
FILTER C
SINX/X
EQUALIZER
SINX/X
EQUALIZER
ALLPASS
FILTER
ALLPASS
FILTER
2X
BUF
2X
BUF
3
ML6423
2
PIN CONFIGURATION
PIN DESCRIPTION
PIN
NAME
FUNCTION
1
V
IN
C
Signal input to filter C. Input
impedance is 4k
W.
2
GND
Power and logic ground.
3
GNDC
Ground pin for filter C.
4
V
CC
Positive supply: 4.5V to 5.5V.
5
NC
No Connect
6
V
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).
7
V
CC
C
Power supply voltage for filter C.
8
V
OUT
B
Sum of Filter A and 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).
9
GNDB
Ground pin for output B.
PIN
NAME
FUNCTION
10
V
CC
B
Power supply voltage for output B.
11
NC
No Connect
12
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).
13
V
CC
A
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
V
IN
A
Signal input to filter A. Input
impedance is 4k
W.
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
TOP VIEW
ML6423
16-Pin Wide SOIC (S16W)
VINC
GND
GNDC
VCC
NC
VOUTC
VCCC
VOUTB
VINA
RANGE
GNDA
VCCA
VOUTA
NC
VCCB
GNDB
ML6423
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
) ...................................... 0.3 to 7V
GND .................................................. 0.3 to V
CC
+0.3V
Logic Inputs ........................................ 0.3 to V
CC
+0.3V
Input Current per Pin ............................................ 25mA
Storage Temperature .................................. 65 to 150C
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%, R
L
=75
W or 150W, V
OUT
= 2V
P-P
for 150
W Load and V
OUT
= 1V
P-P
for 75
W
Load, T
A
= Operating Temperature Range (Notes 1, 2, 3)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
GENERAL
R
IN
Input Impedance
3k
4
5
k
W
DR/R
IN
Input R Matching
2
%
I
BIAS
Input Current
V
IN
= 0.5V, RANGE = low
45
A
V
IN
= 0.0V, RANGE = high
210
A
Differential Gain
V
IN
= 0.8V to 1.5V
at 3.58 & 4.43 MHz
1
%
Differential Phase
V
IN
= 0.8V to 1.5V
at 3.58 & 4.43 MHz
1
deg
V
IN
Input Range
RANGE = Low
0.5
1.5
V
RANGE = High
0.0
1.0
V
Peak Overshoot
2T, 0.7V
P-P
pulse
2.0
%
Crosstalk Rejection
f
IN
= 3.58, f
IN
= 4.43MHz
45
dB
Channel to Channel
f
IN
= 100kHz
3
ns
Group Delay Matching
(f
C
= 5.5MHz)
Channel to Channel
f
IN
= 100kHz
1.5
%
Gain Matching
Output Current
R
L
= 0 (short circuit)
75
mA
C
L
Load Capacitance
35
pF
Composite Chroma/Luma delay
f
C
= 5.5MHz
15
ns
f
C
= 9.6MHz
8
ns
5.50MH
Z
FILTER
Bandwidth (monotonic passband)
0.55dB (Note 4)
4.95
5.50
6.05
MHz
Subcarrier Frequency Gain
f
IN
= 3.58MHz
0.9
1.4
2.3
dB
ML6423-1
f
IN
= 4.43MHz
1.1
1.6
2.5
dB
Attenuation
f
IN
= 10MHz
20
25
dB
f
IN
= 50MHz
45
55
dB
Output Noise
BW = 30MHz
1
mV
RMS
Group Delay
180
ns
ML6423
4
ELECTRICAL CHARACTERISTICS
(Continued)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
5.50MH
Z
FILTER
(Continued)
Small Signal Gain
V
IN
= 100mV
P-P
at 100kHz,
5.5
6
6.5
dB
Filter A or C
Composite (CV) Small Signal Gain
V
IN
A, C = 100mV
P-P
at 100kHz
11
12
13
dB
9.6MH
Z
FILTER
Bandwidth (monotonic passband)
2dB (Note 4)
8.6
9.6
10.6
MHz
Subcarrier Frequency Gain
f
IN
= 3.58MHz
0.1
0.4
1.1
dB
ML6423-2
f
IN
= 4.43MHz
0.1
0.6
1.3
dB
Subcarrier Frequncy Gain
f
IN
= 3.58MHz
0.1
0.4
1.9
dB
ML6423-5
f
IN
= 4.43MHz
0.1
0.6
1.1
dB
Attenuation
f
IN
= 17MHz
20
25
dB
f
IN
= 85MHz
45
55
dB
Output Noise
BW = 30MHz
1
mV
RMS
Group Delay
100
ns
Composite (CV) Small Signal Gain
V
IN
A, C = 100mV
P-P
at 100kHz
11
12
13
dB
I
CC
ML6423-5 Supply Current R
L
= 150
W
V
IN
= 0.5V (Note 5)
140
175
mA
V
IN
= 1.5V
170
215
mA
ML6423-5 V
OUT
A, V
OUT
B sink current
V
IN
= 0.5V
8.3
11.5
mA
ML6423-5 V
OUT
C sink current
V
IN
= 0.5V
4.3
6.5
mA
ML6423-5 Output DC Level
V
IN
= 0.5V, Range = Low
0.5
V
DIGITAL AND DC
V
IL
Logic Input Low
Range
0.8
V
V
IH
Logic Input High
Range
V
CC
0.8
V
I
IL
Logic Input Low
V
IN
= GND
1
A
I
IL
Logic Input High
V
IN
= V
CC
1
A
I
CC
Supply Current R
L
= 150
W
V
IN
= 0.5V (Note 5)
110
135
mA
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 500
W 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: P
D
= (I
CC
V
CC
) [3(V
OUT2
/RL)]
ML6423
5
Figure 1a. Stop-Band Amplitude vs. Frequency
(f
C
= 5.5MHz)
Figure 1b. Stop-Band Amplitude vs. Frequency
(f
C
= 9.6MHz)
Figure 3b. Group Delay vs. Frequency
(f
C
= 9.6MHz)
Figure 3a. Group Delay vs. Frequency
(f
C
= 5.5MHz)
Figure 2b. Pass-Band Amplitude vs. Frequency
(f
C
= 9.6MHz)
Figure 2a. Pass-Band Amplitude vs. Frequency
(f
C
= 5.5MHz)
16
6
4
14
24
34
44
54
64
74
84
AMPLITUDE (dB)
FREQUENCY (Hz)
100K
1M
10M
100M
16
6
4
14
24
34
44
54
64
74
84
AMPLITUDE (dB)
FREQUENCY (Hz)
100K
1M
10M
100M
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
AMPLITUDE (dB)
FREQUENCY (Hz)
100K
1M
10M
5.5MHz
ML6423-1
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
AMPLITUDE (dB)
FREQUENCY (Hz)
100K
1M
10M
5.5MHz
ML6423-2
ML6422-2
220
200
180
160
140
120
100
80
60
40
20
GROUP DELA
Y (ns)
FREQUENCY (Hz)
100K
5.5MHz
10MHz
130
125
120
115
110
105
100
95
90
85
80
GROUP DELA
Y (ns)
FREQUENCY (Hz)
100K
5M
10M
9.3M
ML6423
6
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 75
W 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 75
W 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 75
W 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 4k
W. 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 75
W
or 150
W resistor to ground may need to be added to the
DAC output (filter input).
Figure 4. ML6423 AC Coupled DC Bias Test Circuit
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
V
IN
A
RANGE
GNDA
V
CC
A
V
OUT
A
NC
V
CC
B
GNDB
V
IN
C
GND
GNDC
V
CC
NC
V
OUT
C
V
CC
C
V
OUT
B
75
V
OUT
A
1
F
100
F
0.1
F
85
100
2.56k
1k
V
IN
A
+
+
+
0.1
F
100
F
1nF
1nF
1nF
0.1
F
0.1
F
0.1
F
0.1
F
1nF
1
F
100
F
75
85
100
V
OUT
C
75
V
OUT
B
2.56k
1k
V
IN
C
+5V
FB2
FB1
DC
BIAS
INPUT SIGNAL
= 1V
P-P
0.1
F
1nF
INPUT
DECOUPLING
SUPPLY NOISE
CLAMPING
INPUT
TERMINATION
RESISTOR
ML6423
7
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 V
CC
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:
P
(I
V
)
V
RL
3
D
CC
CC
OUT
2
=
-
!
"
$
#
#
This is a measure of the amount of current the part sinks
(current in current out to the load).
Under worst case conditions:
P
mW
D
=
-
!
"
$
#
#
=
( .
. )
.
.
0 175 5 5
15
75
3
8725
2
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.
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 75
W or
150
W). Resistance values should be adjusted to provide
1V
P-P
at the input of the ML6423. The ML6423 will drive
75
W source termination resistors (making the total load
150
W) so that no external drivers or amplifiers are
required.
Figure 5a. Sinx/x Frequency Response
4
2
0
2
4
AMPLITUDE
FREQUENCY (MHz)
0
1
2
3
4
5
6
7
THEORETICAL SINX/X
CORRECTION FOR
13.5MHz SAMPLING
SINX/X ERROR FOR
TYPICAL DAC AT 13.5MHz
ML6423
8
Figure 6. ML6423 Reconstruction Performance in the Frequency Domain
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%.
Figure 5b. Typical ML6423 Reconstruction Application
Y
DAC
INPUTS
DAC
(CURRENT SOURCING
C
Y
ANALOG
OUTPUTS
CV
C
DAC
(CURRENT SOURCING
ML6423
DAC LOAD
ADJUSTED FOR
1V
P-P
75
75
75
+5V
+
FILTER PERFORMANCE
10
0
10
20
30
40
50
60
0
5
10
15
20
25
FREQUENCY (MHz)
AMPLITUDE (dB)
IDEAL SINX/X RESPONSE
3dB REFERENCE MARKER
A. ML6423 AMPLITUDE RESPONSE
B. SIGNAL DISTORTION SPECTRUM
C. RECONSTRUCTED SIGNAL
SPECTRUM
ML6423
9
Figure 7. ML6423 Reconstruction Performance in the Time Domain
Figure 8. Amplitude Ripple of Reconstructed Swept Pulses
A. OVERSAMPLED
SIGNAL
B. CCIR601 SAMPLED
SIGNAL
C. ML6423 FILTERED
SIGNAL
D. CCIR601 SAMPLED
WAVEFORM
E. ML6423 FILTERED
WAVEFORM
>6%
<1%
A. OVERSAMPLED
WAVEFORMS
B. CCIR601 SAMPLED
WAVEFORMS
C. ML6423
RECONSTRUCTED
WAVEFORMS
ML6423
10
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.
DS6423-01
2092 Concourse Drive
San Jose, CA 95131
Tel: 408/433-5200
Fax: 408/432-0295
www.microlinear.com
PHYSICAL DIMENSIONS
inches (millimeters)
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)
0 - 8
1
0.024 - 0.034
(0.61 - 0.86)
(4 PLACES)
Package: S16W
16-Pin Wide SOIC
ORDERING INFORMATION
PART NUMBER
BW (MH
Z
)
TEMPERATURE RANGE
PACKAGE
ML6423CS-1 (EOL)
5.5/5.5
0C to 70C
16-pin Wide SOIC (S16W)
ML6423CS-2 (EOL)
9.6/9.6
0C to 70C
16-pin Wide SOIC (S16W)
ML6423CS-5 (Obsolete)
9.6/9.6
0C to 70C
16-pin Wide SOIC (S16W)
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