GS1528 HD-LINX II Multi-Rate SDI Dual Slew-Rate

Cable Driver

Data Sheet

16632 - 9

August 2010

7 of 13

3. Detailed Description

3.1 Input Interfacing

SDI/SDI are high-impedance differential inputs (see Figure 2-1 for equivalent input

circuit).

Several conditions must be observed when interfacing to these inputs:

1. The differential input signal amplitude must be between 300 and 2000mVpp.

2. The common mode voltage range must be as specified in Table 1-1: DC Electrical

Characteristics.

3. For input trace lengths longer than approximately 1cm, the inputs should be

terminated as shown in the Typical Application Circuit.

The GS1528 inputs are self-biased, allowing for simple AC-coupling to the device. For

serial digital video, a minimum capacitor value of 4.7μF should be used to allow

coupling of pathological test signals. A tantalum capacitor is recommended.

3.2 SD/HD

The GS1528 SDO rise and fall times can be set to comply with both SMPTE 259M/344M

and SMPTE 292M. For all SMPTE 259M standards, or any data rate that requires longer

rise and fall time characteristics, the SD/HD pin must be set to a HIGH INPUT. For SMPTE

292M standards and signals which require faster rise and fall times, this pin should be

set to a LOW INPUT.

3.3 Output Interfacing

The GS1528 outputs are current mode, and will drive 800mV into a 75Ω load. These

outputs are protected from accidental static damage with internal static protection

diodes.

The SMPTE 292M, SMPTE 344M and SMPTE 259M standards requires that the output of

a cable driver have a source impedance of 75Ω and a return loss of at least 15dB between

5MHz and 1.485GHz.

In order for an SDI output circuit using the GS1528 to meet this specification, the output

circuit shown in the Typical Application Circuit is recommended.

(see the Application Information on page 11 in this data sheet for further details). A

4.7μF capacitor is used for AC-coupling the output of the GS1528. This value is chosen

to ensure that pathological signals can be coupled without a significant DC component

occurring.