GS2993 Dual Output Adaptive Cable Equalizer

Data Sheet

53966 - 4

August 2012

13 of 23

Propietary & Confidential

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

(DC-coupled Output)

(AC-coupled Output)

(DC-coupled Output)

(AC-coupled Output)

3.3V

3.2V

3.1V

3.1V

2.9V

2.5V

2.4V

2.3V

2.3V

2.1V