SGM9154 Datasheet, PDF (7/14 Pages) SG Micro Corp – Single Channel, Video Filter Driver

SGM9154
APPLICATION INFORMATION
Application Circuits
The SGM9154 video filter provides 6dB gain from input to
output. In addition, the input is 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.
For symmetric signals like Chroma, U, V, Pb and Pr, the
average DC bias is fairly constant and the input can be
AC-coupled. DAC output can also drive these same signals
without the AC coupling capacitor.
I/O Configurations
For an AC-coupled DAC drive with AC-coupled output, use
the configuration in Figure 3.
DVD or
STB
SoC
DAC
Output
0V - 1.4V
0.1μF
LCVF
Bias
Active
75Ω ^220μF
Figure 3. AC-Coupled Input and Output
Alternatively, if the DAC’s average DC output level causes the
signal to exceed the range from 0V to 1.4V, it can be
AC-coupled as shown in Figure 4.
DVD or
STB
0V - 1.4V
LCVF
Bias
75Ω
SoC
0.1µF
Active
DAC
Output
Figure 4. AC-Coupled Input, DC-Coupled Output
For a DC-coupled DAC drive with DC-coupled output, use the
configuration in Figure 5.
Single Channel, Video Filter
Driver for HD (1080p)
DVD or
STB
SoC
DAC
Output
0V - 1.4V
LCVF
75Ω
Bias
Inactive
Figure 5. DC-Coupled Input and Output
NOTE: The video tilt or line time distortion is dominated by the
AC coupling capacitor. The value may need to be increased
beyond 220μF to obtain satisfactory operation in some
applications.
Power Dissipation
The SGM9154 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 equations can be used to calculate the power
dissipation and internal temperature rise.
T_J = T_A + P_D • θ_JA
(1)
where:
P_D = V_CC • I_CC - (V_O2/R_L)
(2)
where:
V_O = 2V_IN + 0.35V
(3)
V_IN = RMS value of input signal
I_CC = 15mA
V_CC = 5.0V
R_L = channel load resistance
Board layout can also affect thermal characteristics. Refer to
the Layout Considerations section for details.
The SGM9154 is specified to operate with output currents
typically less than 50mA. Internal amplifiers are current
limited to a maximum of 80mA and should withstand
brief-duration short-circuit conditions. This capability is not
guaranteed.
SG Micro Corp
7
www.sg-micro.com