3. Detailed Description
3.1 Input Interfacing
SDI/SDI are high-impedance differential inputs (see
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
3. For input trace lengths longer than approximately 1cm, the inputs should be
terminated as shown in the
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
is recommended.
The value of L
COMP
will vary depending on the PCB layout, with a typical value of 5.6nH
(see the
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.
GS1528 HD-LINX II Multi-Rate SDI Dual Slew-Rate
Cable Driver
Data Sheet
16632 - 9
August 2010
7 of 13
GENNUM [ GENNUM CORPORATION ]
