GV8601 Datasheet, PDF (8/16 Pages) Semtech Corporation – Adaptive Cable Equalizer

4. Detailed Description
The GV8601 is a high-speed BiCMOS IC designed to equalize serial digital video signals.
The GV8601 can equalize 3Gb/s, HDcctv/HD-SDI and SD-SDI serial digital signals, and
will typically equalize 150m of Belden 543945 HDcctv 1.1 reference cable at 1.485Gb/s
and 140m of Belden 1694A cable at 2.970Gb/s. When used for HD-VLC™ applications at
270Mb/s, the GV8601 will typically equalize signals over 330m of Belden 543945. The
GV8601 is powered from a single +3.3V power supply and consumes approximately
195mW of power.
4.1 Serial Digital Inputs
The Serial Data Signal may be connected to the input pins (SDI/SDI) in either a
differential or single ended configuration. AC coupling of the inputs is recommended, as
the SDI and SDI inputs are internally biased at approximately 1.8V.
4.2 Cable Equalization
The input signal passes through a variable gain equalizing stage, whose frequency
response closely matches the inverse of the cable loss characteristic. In addition, the
variation of the frequency response with control voltage imitates the variation of the
inverse cable loss characteristic with cable length.
The edge energy of the equalized signal is monitored by a detector circuit which
produces an error signal corresponding to the difference between the desired edge
energy and the actual edge energy. This error signal is integrated by both an internal and
an external AGC filter capacitor providing a steady control voltage for the gain stage. As
the frequency response of the gain stage is automatically varied by the application of
negative feedback, the edge energy of the equalized signal is kept at a constant level
which is representative of the original edge energy at the transmitter. The equalized
signal is also DC restored, effectively restoring the logic threshold of the equalized signal
to its correct level independent of shifts due to AC coupling.
4.3 Serial Digital Outputs
The digital output signals have a nominal voltage of 800mV_pp differential, or 400mV_pp
single-ended when terminated with 50Ω as shown in Figure 4-1.
GV8601 Adaptive Cable Equalizer
Final Data Sheet
Rev. 1
November 2012
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