GS9064A Data Sheet
+187.5mV
V
= 2.925V
typical
CM
-187.5mV
+187.5mV
SDO
SDO
50
50
V
= 2.925V
typical
CM
-187.5mV
Figure 4-1: Typical Output Voltage Levels
4.3 Programmable Mute Output and Cable Length Indicator
For SMPTE 259M inputs, the GS9064A incorporates a programmable threshold
output mute (MCLADJ) and an analog cable length indicator (CLI).
MCLADJ
In applications where there are multiple input channels using the GS9064A, it is
advantageous to have a programmable mute output to avoid signal crosstalk.
The output of the GS9064A can be muted when the input signal decreases below
a certain input level. This threshold is determined using the input voltage applied
to the MCLADJ pin. The MCLADJ pin may be left unconnected for applications
where output muting is not required.
This feature has been designed for use in applications such as routers where
signal crosstalk and circuit noise cause the equalizer to output erroneous data
when no input signal is present. The use of a Carrier Detect function with a fixed
internal reference does not solve this problem since the signal to noise ratio on the
circuit board could be significantly less than the default signal detection level set by
the on chip reference.
CLI
The output voltage of the CLI pin is an approximation of the amount of cable
present at the GS9064A input. With 0m of cable, 800mV input signal levels, and a
data rate of 270Mb/s, the CLI output voltage is approximately 2.5V. As the cable
length increases, the CLI voltage decreases providing an approximate correlation
between the CLI voltage and cable length.
37325 - 0 December 2005
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GENNUM [ GENNUM CORPORATION ]
