
2005 Fairchild Semiconductor Corporation
www.fairchildsemi.com
FMS6363 Rev. 1.0.4
6
FM
S6363
—
Low-
C
ost
,Three-
C
h
annel,6t
h
-O
rder,
H
igh-
D
e
finit
ion,
Video
Filt
er
D
river
The same method can be used for biased signals with
the addition of a pull-up resistor to make sure the clamp
never operates. The internal pull-down resistance is
800k
Ω ±20%, so the external resistance should be
7.5M
Ω to set the DC level to 500mV. If a pull-up
resistance of less than 7.5M
Ω desired, add an external
pull-down such that the DC input level is set to 500mV.
75
Ω
LCVF
Bias
Input
75
Ω
0.1
External Video
source must
be AC-coupled.
500mV+/-350mV
7.5M
Ω
Figure 13. Biased SCART with DC-coupled Outputs
DVD or
STB
SoC
DAC
Output
75
Ω
LCVF
Clamp
Inactive
0V- 1.4V
220
Figure 14. DC-coupled Inputs, AC-coupled Outputs
75
Ω
LCVF
Clamp
Active
75
Ω
0.1
External video
source must
be AC-coupled.
220
500mV+/-350mV
7.5M
Ω
Figure 15. Biased SCART with AC-Coupled Outputs
Note
: The video tilt or line time distortion is dominated
by the AC-coupling capacitor. The value may
need to be increased beyond 220F to obtain
satisfactory operation in some applications.
Power Dissipation
The FMS6363 output drive configuration must be
considered when calculating overall power dissipation.
Care must be taken not to exceed the maximum die
junction temperature. The following example can be
used to calculate the FMS6363’s power dissipation and
internal temperature rise.
TJ= TA+ Pd ΘJA
where Pd= PCH1+ PCH2+ PCH3
and PCHx= VS ICH- (VO2/RL)
where
VO = 2VIN+ 0.280V
ICH = (ICC/ 3) + (VO/RL)
VIN= RMS value of input signal
ICC = 24mA
VS= 5V
RL= channel load resistance
(1)
Board layout affects thermal characteristics. Refer to
the Layout Considerations section for more information
.
The FMS6363 is specified to operate with output
currents typically less than 50mA, more than sufficient
for a single (150
Ω) video load. Internal amplifiers are
current limited to a maximum of 100mA and should
withstand
brief
duration,
short-circuit
conditions;
however, this capability is not guaranteed.
Output Considerations
The FMS6363 outputs will be DC offset from the input
by 150mv therefore VOUT = 2*VIN DC+150mv. This offset
is required to obtain optimal performance from the
output driver and is held at the minimum value in order
to decrease the standing DC current into the load.
Since the FMS6363 has a 2x (6dB) gain, the output is
typically connected via a 75 series back-matching
resistor followed by the 75 video cable. Because of
the inherent divide by two of this configuration, the
blanking level at the load of the video signal is always
less then 1V. When AC-coupling the output ensure that
the coupling capacitor of choice will pass the lowest
frequency content in the video signal and that line time
distortion (video tilt) is kept as low as possible.
The selection of the coupling capacitor is a function of
the subsequent circuit input impedance and the leakage
current of the input being driven. In order to obtain the
highest
quality
output
video
signal
the
series
termination resistor must be placed as close to the
device output pin as possible. This greatly reduces the
parasitic capacitance and inductance effect on the
FMS6646 output driver. Recommend distance from
device pin to place series termination resistor should be
no greater than 0.1 inches.
Figure 16.Distance from Device Pin to Series
Termination Resistor