GS2993 Datasheet, PDF (13/23 Pages) Gennum Corporation – Automatic power-down on loss of signal

4. Detailed Description
The GS2993 is a high-speed BiCMOS IC designed to equalize serial digital signals.The
GS2993 can equalize 3Gb/s, HD and SD serial digital signals, and will typically equalize
140m of Belden 1694A cable at 2.97Gb/s, 220m at 1.485Gb/s and 400m at 270Mb/s. The
GS2993 can be powered from a single +3.3V power supply. When using 1.2V CML, the
GS2993 typically consumes approximately 200mW of power. The GS2993 features dual
independently controlled outputs, and can be operated from a single +3.3V power
supply.
4.1 Serial Data Inputs
The Serial Data signal can 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 GS2993 features dual independently controlled outputs. The digital output signals
have a nominal voltage of either 800mVp-p or 400mVp-p, as set by the OP1_CTL pin for
SDO1 and OP2_CTL pin for SDO2.
Table 4-1 below shows the typical output voltage levels across different common mode
voltages and swing values.
Table 4-1: Typical Output Voltage Levels
Supply Voltage -
Output Driver
3.3V
2.5V
400mV_p-p Swing
400mV_p-p Swing
800mV_p-p Swing
800mV_p-p Swing
(DC-coupled Output) (AC-coupled Output) (DC-coupled Output) (AC-coupled Output)
3.2V
2.4V
3.1V
2.3V
3.1V
2.3V
2.9V
2.1V
GS2993 Dual Output Adaptive Cable Equalizer
Data Sheet
53966 - 4
August 2012
13 of 23
Propietary & Confidential