MAX11503 View Datasheet(PDF) - MAXWELL TECHNOLOGIES
Part Name
Description
Manufacturer
MAX11503 Datasheet PDF : 8 Pages
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Video Y/C Summer with
Driver and Chroma Mute
Applications Information
Input Configuration
The luma input can be DC-coupled if the sync tip is near
ground (see the Minimum Supply-Voltage Considerations
section). Otherwise, it should be AC-coupled into YIN
with a 0.1µF capacitor. When the luma input is AC-cou-
pled, the transparent clamp adjusts its sync tip to
ground at YIN. Because the chroma input is internally
AC-coupled and biased, an external AC-coupling
capacitor is not required unless the signal is outside
the operating voltage range.
Output-Amplifier Configuration
The output buffer is capable of driving two terminated
AC- or DC-coupled 75Ω video coax cables. With sync
tip at the input at ground, the sync tip at the output is
offset by +250mV.
MAX11503
COUT
68µF*
75Ω
OUT
75Ω
SAG
CSAG
33µF*
*REMOVE AND SHORT FOR DC-COUPLED OPERATION
SAG-Corrected Output
SAG uses feedback to reduce the size of the output AC-
coupling capacitor. Without SAG, a 220µF AC-coupling
capacitor is required to reduce tilt when feeding each
terminated 75Ω coax cable (Figure 2). This sets the
highpass -3dB frequency to 5Hz. Using SAG correction
with COUT = 68µF and CSAG = 33µF also achieves a
highpass -3dB frequency of 5Hz, but with smaller
capacitors (Figure 1).
SAG correction is inherently designed to drive a con-
stant load because the capacitor values vary with the
number of loads driven. If the capacitors are chosen for
two loads and the end user only connected one, the
video tilt would be opposite in sign, but of the same
magnitude as not using SAG at all. This would cause
excessive video tilt and the failure of the next piece of
equipment. The recommended capacitor values for two
constant 75Ω terminated video loads are COUT =
120µF, CSAG = 68µF. In addition, SAG feedback pre-
distortion function requires about 30% more overhead
in the video driver. Hence, use SAG correction only
with a typical 5V supply voltage. See the Minimum
Supply-Voltage Considerations section for calculations.
When SAG is not used, such as with AC- or DC-coupling
at the output, the driver can drive two terminated 75Ω
video coaxial cables. Connect SAG to OUT when not
using SAG correction.
Traditional AC-Coupled Output
The MAX11503 can also be configured to drive one or
two of the familiar terminated AC-coupled video coax
cables as shown in Figure 2.
Figure 1. Output with SAG Correction
75Ω 220µF*
MAX11503
75Ω 220µF*
MAX11503
75Ω
OUT
OUT
75Ω
75Ω 220µF*
SAG
SAG
75Ω
*REMOVE AND SHORT FOR DC-COUPLED OPERATION
(a)
(b)
Figure 2. Traditional AC-Coupled Output
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