FMS6413
REV. 1.0.2 6/27/02
3
Functional Description
Introduction
The FMS6413 is a monolithic continuous time video filter -
driver designed for reconstructing the video signals from a
D/A source. This chip is intended for use in applications
with AC coupled input and AC coupled outputs. (See
Figure 1) The reconstruction filter approximates a 4th-order
Butterworth characteristic with an optimization toward low
over-shoot and flat group delay. The video output is capable
of driving 2VP-P into an AC coupled 150
Ω
video load, with
up to 35pF of load capacitance at the output pin. The channel
is clamped during sync to establish the appropriate output
voltage swing range. Thus the input coupling capacitor does
not behave according to the conventional RC time constant.
Clamping for the video channel settles to less than 10mv
within 5ms of a change in video input source. In most
applications the input coupling capacitor is 0.1µF. The input
typically sinks 1µA during active video, which nominally
tilts a horizontal line by about 2mV at the Video output.
During sync, the clamp typically sources 20µA to restore the
DC level. The net result is that the average input current is
zero. Any change in the input coupling capacitor’s value will
inversely alter the amount of tilt per line. Such a change will
also linearly affect the clamp response time. This product is
robust and stable under all stated load and input conditions.
Capacitive bypassing VCC directly to ground ensures this
performance.
Video I/O
The video input is driven by either a low impedance source
of 1VP-P or the output of a 75
Ω
terminated line. The input is
required to be AC coupled via a 0.1µF coupling capacitor
which allows for a settling time of 5ms. The video output is
capable of driving an AC coupled 150
Ω
load at 2VP-P, or
1VP-P into a 75
Ω
load. Up to 35pF of load capacitance
(at the output pin) can be driven without stability or slew
issues. The output is AC coupled with a 220µF or larger AC
coupling capacitor.
Typical Applications Diagram
Figure 1.
1
NC (Reserved)
2
3
GND_VIDEO
4
NC (Reserved) NC (Reserved)
NC (Reserved)
VCC_VIDEO
8
7
6
5
FMS6413
SYNC STRIP,
REF, AND TIMING
gM
x2
1V
VIDEO_IN
VIDEO_IN VIDEO_OUT
VIDEO_OUT
0.1µF
220µF
1µF
0.1µF
Video Cable
75Ω
75Ω
+5.0V
