Figure 1. MAX7428 Typical Application Circuit
MAX7428/MAX7430/MAX7432A
Detailed Description
The MAX7428/MAX7430/MAX7432A filter and buffer the
outputs of DAC encoder chipsets that process digital
video information in applications such as set-top boxes,
hard-disk recorders, DVD players, recorders, and digi-
tal VCRs. These devices also filter and “clean-up” ana-
log video signals. Each channel in the MAX7428/
MAX7430/MAX7432A includes an input mux to select
the input channel, a 6th-order Sallen-Key filter with four
adjustable high-frequency boost levels, an output
buffer with a 6dB gain, a sync detector and clamp, and
an external resistor to set internal bias levels. Output
disable adds additional multiplexing in a wired-OR con-
figuration. Filter bypass, in conjunction with the two
inputs, can be used to provide filtered and unfiltered
video signal processing. Maxim’s Single Pin Bus
(MSPB) interface controls all of the above features. An
external capacitor is used to assign each device a
unique address that allows control of up to 16 devices
on the same bus. Typical application circuits for the
MAX7428/MAX7430/MAX7432A are shown in Figures 1,
2, and 3.
Input Considerations
Use a 0.1µF ceramic capacitor to AC-couple the input
to the MAX7428/MAX7430/MAX7432A. This input
capacitor stores a DC level to level-shift the input signal
to an optimal point between V
CC
and GND. The ABSEL
bit on the Control Register sets which channel (IN_A or
IN_B) is selected (Control Register section). The IN_A
and IN_B inputs have a typical input resistance of
50kΩ.
Standard Definition Video Reconstruction
Filters and Buffers
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Pin Description (continued)
