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. The digital output signals
have a nominal voltage of 750mV
pp
differential, or 375mV
pp
single ended when
terminated with 50Ω as shown in
+187.5mV
V
CM
= 2.925V
typical
SDO
-187.5mV
SDO
50
50
+187.5mV
V
CM
= 2.925V
typical
-187.5mV
Figure 4-1: Typical Output Voltage Levels
4.3 Programmable Mute Output and Cable Length Indicator
For SMPTE 259M inputs, the GS1524A incorporates a programmable threshold output
mute (MCLADJ) and an analog cable length indicator (CLI).
GS1524A Adaptive Cable Equalizer
Data Sheet
28852 - 5
June 2009
11 of 16
GENNUM [ GENNUM CORPORATION ]
