gs2914 Gennum Corporation, gs2914 Datasheet - Page 8

• Manufacturer Part Number: gs2914
• Description: Gs2914 Hd-linx? Iii Serial Digital Dc Restorer For Fibre-optic Receivers
• Manufacturer: Gennum Corporation

4. Detailed Description
The GS2914 is a high speed BiCMOS IC designed to amplify and DC restore serial digital
signals.
The GS2914 can DC restore serial digital signals, and will typically restore signals as low
as 10mV. The GS2914 is powered from a single +3.3V power supply and consumes
approximately 150mW 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 Programmable Input Signal Strength Adjust (ISSADJ)
For SMPTE 259M inputs, the GS2914 incorporates a programmable Input Signal
Strength Adjust (ISSADJ) threshold.
This feature can be useful in applications where there are multiple input channels using
the GS2914 and the maximum gain can be limited to avoid crosstalk.
The ISSADJ pin acts to change the threshold of the Carrier Detect (CD) pin. When the
input signal drops below a certain threshold, the CD pin will be driven high, indicating
that there is not a valid input signal. By increasing the voltage level at ISSADJ, the
threshold at which the carrier is detected is increased, or CD will be driven HIGH at a
higher input amplitude level. Decreasing the voltage will decrease the threshold at
which carrier is detected.In order to enable automatic muting of the output of the
GS2914, the CD pin should be connected directly to the MUTE pin. In applications where
programmable input signal swing adjust is not required, the ISSADJ pin may be left
unconnected.
3.3V
MUTE
2.5V
10mV
1V
Input Amplitude
Figure 4-1: ISSADJ Muting Characteristics
GS2914 HD-LINX™ III Serial Digital DC Restorer for
8 of 14
Fibre-Optic Receivers
Data Sheet
50864 - 0
February 2009