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 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).
+5V
+
0.1µF
1nF
100µF
FB2
SUPPLY NOISE
CLAMPING
100Ω
100Ω
INPUT
DECOUPLING
0.1µF
V
IN
C
INPUT SIGNAL
= 1V
P-P
85Ω
+
100µF
1µF
2.56kΩ
1µF
100µF
+
85Ω
V
IN
A
2.56kΩ
1
DC
BIAS
1kΩ
2
GND
RANGE
15
V
IN
C
V
IN
A
16
1k
0.1µF
INPUT
TERMINATION
RESISTOR
FB1
0.1µF
1nF 3
GNDC
GNDA
14 0.1µF
4
V
CC
V
CC
A
13
1nF
5
V
OUT
C
75Ω
0.1µF 7
V
OUT
B
75Ω
1nF
NC
V
OUT
A
12
75Ω
11
V
OUT
A
6
V
OUT
C
NC
V
CC
C
V
CC
B
10 0.1µF
8
V
OUT
B
GNDB
9
1nF
Figure 4. ML6423 AC Coupled DC Bias Test Circuit
6
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
