SGM9114_16 Datasheet, PDF (7/11 Pages) SG Micro Corp – 8MHz, 5th-Order Video Driver

SGM9114
APPLICATION INFORMATION
The SGM9114 low cost, integrated, 5th-order video
filter is intended to replace passive LC filters and
drivers in low voltage portable video applications.
The SGM9114 input must be AC-coupled because the
input capacitor stores the clamp voltage. It needs a
typical value of 0.1µF for the input clamp to meet the
Line Droop specification. The SGM9114 output can
drive an AC- or DC-coupled doubly terminated coax
(150Ω) load (see Figure 1). DC coupling the output
removes the need for an expensive and large output
coupling capacitor (see Figure 2). If an AC-coupled
output is needed, the SAG correction circuit can be
used to reduce the AC output coupling capacitor value.
Offering SAG correction, fixed gain of 6dB, and a
5th-order low pass filter in a tiny space saving package
makes the SGM9114 well suited for space sensitive
applications such as digital cameras, cellular phones
and other portable devices.
Enable/Shutdown
The SGM9114 has a shutdown feature that disables
the output and reduces the quiescent current to 0.1μA.
This feature is particularly useful in portable
applications, such as video cameras, hand held gaming
devices and cellular phones, where video filtering and
driving capability are required.
8MHz, 5th-Order Video Driver
with 6dB Gain
Internal Sync Clamp
The typical embedded video DAC operates from a
ground referenced single supply. This becomes an
issue because the lower level of the sync pulse output
may be at a 0V reference level to some positive level.
The problem is that presenting a 0V input to most
single supply driven amplifiers will saturate the output
stage of the amplifier, resulting in a clipped sync tip and
degrading the video image. A larger positive reference
may offset the input above its positive range.
The SGM9114 features an internal sync clamp and
offset function to level shift the entire video signal to the
best level before it reaches the input of the amplifier
stage. These features are also helpful to avoid
saturation of the output stage of the amplifier by setting
the signal closer to the optimal voltage range.
The typical application of the SGM9114 is shown in
Figure 1. The AC-coupled video sync signal is pulled
negative by a current source at the input of the
comparator amplifier. When the sync tip goes below the
comparator threshold, the comparator output is driven
negative, and the PMOS device turns on, clamping
sync tip to near ground level. The network triggers on
the sync tip of video signal.
IN
R_IN
0.1µF
C_IN
V_CC = 3.0V to 5.5V
To External Power
Supply or Control I/O
10kΩ
V_CC
DISABLE
5th-Order
Filter
Level
Shifter
OUT
6dB
SGM9114
GND
SAG
C_OUT
47µF
C_S
22µF
R_OUT
75Ω _{75Ω RL}
Figure 1. AC-Coupled Input/AC-Coupled Output
SG Micro Corp
7
www.sg-micro.com