MAX11506/MAX11507
Detailed Description
The MAX11506/MAX11507 integrated filters offer 6 chan-
nels, 3 for SD video and 3 for either SD or HD video and
include +6dB output buffers on each channel. Each
channel of the MAX11506/MAX11507 contains a trans-
parent input clamp, a 9.0MHz 5th-order lowpass filter
and an output amplifier with a gain of 2V/V (see the
Typical Operating Circuit
). The MAX11506 provides a flat
passband response and the MAX11507 provides a
0.8dB high-frequency boost at 5MHz on all SD-only
channels to help with system roll-off. The SD-only chan-
nels add 280mV of offset at the output.
Three channels, SD/HD1, SD/HD2, and SD/HD3 include
selectable SD and HD video filters, each with a trans-
parent input clamp, a 6th-order lowpass filter with a -3dB
bandwidth of 9.0MHz (SD) and 33MHz (HD), and an
output amplifier with a gain of 2V/V. The SD/HD chan-
nels add 550mV of offset at the output.
The output voltage equations are:
V
SDOUT
= (2 x V
IN
) + 0.28V
V
SD/HDOUT
= (2 x V
IN
) + 0.55V
Typical voltage waveforms are shown in Figures 1 and 2.
Inputs
Transparent Clamps
All inputs feature transparent clamps to allow either AC-
or DC-coupling of the inputs. The clamp remains inac-
tive while the input signal is above ground, offering true
DC input coupling. When the signal goes below
ground, as is the case when it is AC-coupled, the
clamp sets the sync tip close to the ground level.
Input Coupling
The choice of AC- or DC-coupling the input depends
on the video source. Many DACs have a current output
and are terminated to ground with a resistor; such sig-
nals are conveniently DC-coupled. Use AC-coupling
when the DC level of the video signal is unknown or
outside the specified input range of the MAX11506/
MAX11507, such as SCART or V
CC
-terminated DAC
outputs.
DC-Coupled Inputs
When the input is DC-coupled, the voltage must remain
above zero but should not exceed 1.4V (typical).
Low-Cost, 6-Channel SD Plus HD/SD
Selectable Video Filters and Buffers
6 _______________________________________________________________________________________
Pin Description
Frequency-Select Input. SD/HD select for channels 4, 5, and 6. Force FSEL high to select HD, and
low to select SD. Do not leave unconnected.
