Rainbow Electronics MAX7442 - Manual (Page 5)

MAX7440/MAX7441/MAX7442
6-Channel Integrated Video Reconstruction
Filters
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Pin Description
PIN NAME FUNCTION
1 IN1 Channel 1 Filter Input (Optional Boosted Channel)
2 IN2 Channel 2 Filter Input
3 IN3 Channel 3 Filter Input
4 V CC +5V Power Supply. Bypass to GND with a 0.1µF and 1µF capacitor.
5 IN4 Channel 4 Filter Input
6 IN5 Channel 5 Filter Input (Optional Boosted Channel)
7 IN6 Channel 6 Filter Input (Optional Boosted Channel)
8 OUT6 Channel 6 Filter Output
9 OUT5 Channel 5 Filter Output
10 OUT4 Channel 4 Filter Output
11 GND Ground
12 OUT3 Channel 3 Filter Output
13 OUT2 Channel 2 Filter Output
14 OUT1 Channel 1 Filter Output
Detailed Description
The MAX7440/MAX7441/MAX7442 filter the outputs of
DAC encoder chipsets that process digital video infor-
mation in applications such as set-top boxes, hard disk
recorders, DVD players, DVD recorders, and digital
VCRs. These devices also filter and clean up analog
video signals by rejecting out-of-band noise. Each
channel in the MAX7440/MAX7441/MAX7442 includes
a 4th-order lowpass filter and a gain of +1V/V output
stage, as shown in the Typical Application Circuit.
Filter
Filter Response
Each channel of the reconstruction filter consists of a
4th-order Sallen-Key filter configured as two 2nd-order
stages. The filter features a maximally flat passband for
NTSC, PAL, and SDTV bandwidths. The stopband
offers typically 45dB of attenuation at sampling fre-
quencies of 27MHz and above (see Typical Operating
Characteristics). The filter exhibits a Butterworth-type
response resulting in excellent group delay deviation
performance.
High-Frequency Boost
The high-frequency (HF) boost compensates for signal
degradation and rolloff in the signal path prior to the fil-
ter. This performance increases the image sharpness.
The MAX7441/MAX7442 offer a high-frequency boost
on channels OUT1, OUT5, and OUT6.
Output Stage
The output stages of the MAX7440/MAX7441/MAX7442
are designed to drive 1V
P-P signals into high-imped-
ance (>5k Ω) loads. They require external buffers to
drive standard video cables. Most standard audio/
video switching devices include these buffers for STB
applications.
Applications Information
MAX7440/MAX7441/MAX7442 with an A/V
Switching Device
The MAX7440/MAX7441/MAX7442 are designed to
directly interface to an audio/video switching device
used in video applications (i.e., STBs) with SCART
interfaces (see Typical Application Circuit). The output
of the analog filters can drive the high-impedance load
of the switching device. The switching device provides
the buffering to drive standard 150
Ω video loads.
MAX7440/MAX7441/MAX7442 with
External Buffers
External buffering is required for the MAX7440/
MAX7441/MAX7442 to drive standard 150
Ω video
loads. Figure 1 shows the MAX4394 triple op amp, con-
figured with a gain of +2V/V to drive standard video
loads from the MAX7440/MAX7441/MAX7442.