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PDF FMS6246 Data sheet ( Hoja de datos )
| Número de pieza | FMS6246 | |
| Descripción | 6th Order SD/PS Video Filter Driver | |
| Fabricantes | Fairchild Semiconductor | |
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July 2005
FMS6246
Six Channel, 6th Order SD/PS Video Filter Driver
Features
Description
■ Three selectable sixth-order 8/15MHz (SD/PS) filters
■ Three fixed sixth-order 8MHz (SD) filters
■ Transparent input clamping
■ Single video load drive (2Vpp, 150Ω, AV = 6dB)
■ AC or DC-coupled inputs
■ AC or DC-coupled outputs
■ DC-coupled outputs eliminate AC-coupling capacitors
■ Low Power
■ 5V only
■ Robust (12kV HBM) output ESD protection
■ Lead (Pb) Free packages- TSSOP-20
Applications
■ Cable and Satellite set top boxes
■ DVD players
■ HDTV
■ Personal Video Recorders (PVR)
■ Video On Demand (VOD)
The FMS6246 Low Cost Video Filter (LCVF) is intended to
replace passive LC filters and drivers with a low-cost integrated
device. Six 6th order Butterworth filters provide improved image
quality compared to typical passive solutions. The combination
of low power Standard Definition (SD) and Progressive Scan
(PS) filters greatly simplify DVD video output circuitry. Three
channels offer fixed SD filters while the other three are select-
able between SD and PS filters.
The FMS6246 offers a fixed gain of 6dB. A metal option is avail-
able that provides a fixed gain of 9dB, offering even more flexi-
bility.
The FMS6246 may be directly driven by a DC-coupled DAC out-
put or an AC-coupled signal. Internal diode clamps and bias cir-
cuitry may be used if AC-coupled inputs are required (see
applications section for details).
The outputs can drive AC or DC-coupled single (150Ω) video
loads. DC-coupling the outputs removes the need for output
coupling capacitors. The input DC levels will be offset approxi-
mately +280mV at the output.
www.DataSheet4U.com
Block Diagram
SD IN1
SD IN2
SD IN3
SD/PS IN1
Transparent Clamp
6dB
Transparent Clamp
6dB
Transparent Clamp
8MHz, 6th order
6dB
Transparent Clamp
6dB
SD/PS IN2
Transparent Clamp
6dB
SD/PS IN3
Transparent Clamp
FcSEL SD / PS
Selectable
8/15 MHz
6th order
6dB
SD OUT1
SD OUT2
SD OUT3
SD/PS OUT1
SD/PS OUT2
SD/PS OUT3
©2004 Fairchild Semiconductor Corporation
FMS6246 Rev. 1A
1
www.fairchildsemi.com
1 page  
Applications Information
Functional Description
The FMS6246 Low Cost Video Filter (LCVF) provides 6dB gain
(9dB optional, contact factory for further information) from input
to output. In addition, the input will be slightly offset to optimize
the output driver performance. The offset is held to the minimum
required value to decrease the standing DC current into the
load. Typical voltage levels are shown in the diagram below.
1.0 -> 1.02V
0.65 -> 0.67V
0.3 -> 0.32V
0.0 -> 0.02V
Vin
2.28V
1.58V
0.88V
0.28V
Vout
Driven by:
DC-Coupled DAC Outputs or
AC-Coupled and Clamped
Y, R, G, B, CV
There will be a 280mV offset from the DC input level to
the DC output level.
Vout = 2 * Vin + 280mV
coupling capacitor. A conceptual illustration of the input clamp
circuit is shown below:
0.65V
YIN
YOUT
Driver
800kΩ
Figure 2. Input Clamp Circuit
I/O Configurations
For DC-coupled DAC drive with DC-coupled outputs, use this
configuration:
DVD or
STB
SoC
DAC
Output
0V - 1.4V
LCVF
Clamp
Inactive
75
0.85V
0.5V
0.15V
Vin
1.98V
1.28V
0.58V
Vout
Driven by:
DC-Coupled DAC Outputs
AC-Coupled and Biased
U, V, Pb, Pr, C
Figure 1. Typical Voltage Levels
The FMS6246 provides an internal diode clamp to support AC-
coupled input signals. If the input signal does not go below
ground, the input clamp will not operate. This allows DAC out-
puts to directly drive the FMS6246 without an AC coupling
capacitor. The worst-case sync tip compression due to the
clamp will not exceed 7mV. The input level set by the clamp
combined with the internal DC offset will keep the output within
its acceptable range. When the input is AC-coupled, the diode
clamp will set the sync tip (or lowest voltage) just below ground.
For symmetric signals like C, U, V, Cb, Cr, Pb and Pr, the aver-
age DC bias is fairly constant and the inputs can be AC-coupled
with the addition of a pull-up resistor to set the DC input voltage.
DAC outputs can also drive these same signals without the AC
Figure 3. DC-coupled Inputs and Outputs
Alternatively, if the DAC’s average DC output level causes the
signal to exceed the range of 0V to 1.4V, it can be AC-coupled
as follows:
DVD or
STB
SoC
DAC
Output
0V - 1.4V
0.1u
LCVF
Clamp
Active
75
Figure 4. AC-coupled Inputs, DC-coupled Outputs
When the FMS6246 is driven by an unknown external source or
a SCART switch with its own clamping circuitry the inputs
should be AC-coupled as follows:
External Video
source must
be AC-coupled.
0V - 1.4V
0.1u
LCVF
Clamp
Active
75
75
Figure 5. SCART Configuration with DC-coupled
Outputs
FMS6246 Rev. 1A
5 www.fairchildsemi.com
5 Page | ||
| Páginas | Total 10 Páginas | |
| PDF Descargar | [ Datasheet FMS6246.PDF ] | |
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