GS2964 Adaptive Cable Equalizer

Data Sheet

51913 - 3

March 2010

10 of 17

4. Detailed Description

The GS2964 is a high-speed BiCMOS IC designed to equalize serial digital signals.

The GS2964 can equalize 3Gb/s, HD and SD serial digital signals, and will typically

equalize 100m of Belden 1694A cable at 2.97Gb/s, 140m at 1.485Gb/s and 180m at

270Mb/s.The GS2964 is powered from a single +3.3V power supply and consumes

approximately 215mW 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

single-ended when terminated with 50Ω as shown in Figure 4-1.