GS1528 Data Sheet

16632 - 5

June 2005

7 of 13

3. Detailed Description

3.1 Input Interfacing

SDI/SDI are high impedance differential inputs. (See Figure 2-1 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 the 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 75

Ω 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 75

Ω 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.

5.6nH (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.