GS1528B
SDO
SDO
Figure 5-3: Static Protection Diodes
5.3 Output Return Loss Measurement
To perform a practical return loss measurement, it is necessary to force the GS1528B
output to a DC high or low condition. The actual measured return loss will be based on
the outputs being static at VCC or VCC-1.6V. Under normal operating conditions the
outputs of the device swing between VCC-0.4V and VCC-1.2V.
5.4 Output Amplitude Adjustment
The output amplitude of the GS1528B can be adjusted by changing the value of the RSET
resistor as shown in Table 5-1. For an 800mVp-p output with a nominal ±7% tolerance, a
value of 750Ω is required. A ±1% SMT resistor should be used.
The RSET resistor is part of the high speed output circuit of the GS1528B. The resistor
should be placed as close as possible to the RSET pin. In addition, the PCB capacitance
should be minimized at this node by removing the PCB groundplane beneath the RSET
resistor and the RSET pin.
Table 5-1: RSET vs VOD
RSET R (Ω)
Output Swing (mVp-p)
995
824
750
680
573
608
734
800
884
1040
NOTE: For reliable operation of the GS1528B over the full temperature range, do not use an
value below 573Ω.
R
SET
GS1528B HD-LINX® II Multi-Rate Dual Slew-Rate Cable
10 of 14
Driver
Data Sheet
39623 - 4
August 2010
GENNUM [ GENNUM CORPORATION ]
