ML6426
FUNCTIONAL DESCRIPTION
The ML6426 is a triple monolithic continuous time video
filter designed for reconstructing video signals from an
YUV/RGB video D/A source. The ML6426 is intended for
use in AC coupled input and output applications.
An external CMOS compatible H
pulse is required
SYNC
which is Active High on the SYNC IN Pin. See Figure 2.
During sync, the feedback clamp sources/sinks current to
restore the DC level. The net result is that the average
input current is zero. Any change in the input coupling
capacitors' value will linearly affect the clamp response
times.
The filters approximate a 4th-order Butterworth
characteristic with an optimization toward low overshoot
and flat group delay. All outputs are capable of driving
2V into AC coupled 150W video loads, with up to 35pF
P-P
of load capacitance. All outputs are capable of driving a
Each channel is essentially tilt-free. Each input is
clamped by a feedback amp which responds to the output
during sync.
75W load at 1V
.
P-P
All channels are clamped during sync to establish the
appropriate output voltage swing range (DC restore). Thus
the input coupling capacitors do not behave according to
the conventional RC time constant. In most applications,
the ML6426's input coupling capacitors are only 0.1µF.
The ML6426 is robust and stable under all stated load and
input conditions. Bypassing both V pins directly to
CC
ground ensures this performance.
5V
5V
4
12
V
V
CC
CCO
R
R
A/Y
B/Y
A
IN
IN
220µF
220µF
2
5
R
/Y
R
75Ω
75Ω
OUT OUT
0.1µF
0.1µF
4th-ORDER
FILTER A
MUX
MUX
MUX
B
×2
×2
13
11
IN
IN
R
IN
+
TRANSCONDUCTANCE
ERROR AMP
G
G
A/U
A
IN
IN
IN
–
0.5V
G
/U
G
6
7
OUT OUT
4th-ORDER
FILTER B
B/U
B
IN
G
IN
+
–
TRANSCONDUCTANCE
ERROR AMP
0.5V
0.5V
B
B
A/V
A
IN
IN
IN
220µF
B
/V
OUT OUT
75Ω
B
8
9
4th-ORDER
FILTER C
0.1µF
×2
10
B/V
B
IN
B
IN
+
–
TRANSCONDUCTANCE
ERROR AMP
A/B MUX
1
SYNCIN
ACTIVE HIGH
SYNC IN
16
DISABLE
15
GNDO
14
GND
3
Figure 1. Typical Application Schematic
V
= 2.5V
= 1.0V
IH
50% x V
SYNC IN
V
IL
PW
MIN
= 2µS
Figure 2. SYNC IN Pulse Width
6
November, 1999
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
