GS2989

Final Data Sheet

Rev.6

GENDOC-052133

July 2015

10 of 20

Semtech

www.semtech.com

4. Detailed Description

4.1 Serial Data Input

The GS2989 features a differential input buffer with on-chip 100

Ω differential

termination.

The serial data input signal is connected to the DDI and DDI input pins of the device.

Input signals can be single-ended or differential, DC or AC-coupled.

The serial data input buffer is capable of operation with any binary coded signal that

meets the input signal level requirements, in the range of 270Mb/s to at least 2.97Gb/s.

The input circuit is self-biasing to allow for simple AC or DC-coupling of input signals to

the device.

4.2 Input Trace-Equalization

The GS2989 features fixed trace-equalization to compensate for PCB trace dielectric

losses.

Note: This feature is not available in SD mode, and therefore trace-equalization must be

disabled when operating in this mode.

The trace-equalization has two settings, OFF and ON. ON invokes a typical 3dB gain

value at 1.5GHz. This value is optimized for compensating the high-frequency losses

associated with approximately 10 inches of 5-mil stripline in FR4 material.

4.3 Serial Data Output

The GS2989 features dual current-mode differential output drivers capable of driving up

to 1800mVpp single-ended into a 1m length of 75

Ω cable terminated at both ends.

The output signal amplitude or swing is user configurable using an external RSET

resistor.

The SDO1/SDO1 and SDO2/SDO2 pins of the device provide the serial data outputs.

Table 4-1: Input Trace-Equalization

EQ_EN

Function

0

Typical 3dB Trace Equalization

1

Trace Equalization OFF

Floating

Trace Equalization OFF