GS9077 Data Sheet
4.2.1 Output Amplitude (RSET)
The output amplitude of the GS9077 can be adjusted by changing the value of the
R
SET
resistor as shown in
For an 800mV
p-p
output with a nominal ±7%
tolerance, a value of 750Ω is required. A ±1% SMT resistor should be used.
The R
SET
resistor is part of the high speed output circuit of the GS9077. The
resistor should be placed as close as possible to the R
SET
pin. In addition, the PCB
capacitance should be minimized at this node by removing the PCB groundplane
beneath the R
SET
resistor and the R
SET
pin.
Table 4-1: R
SET
vs V
OD
R
SET
R (Ω)
995
824
750
680
573
Output Swing (mVp-p)
608
734
800
884
1040
NOTE: For reliable operation of the GS9077 over the full temperature range, do not use an R
SET
value below 573Ω.
4.2.2 Output Disable
The serial output disable (DISABLE), disables power to the current mode serial
digital output driver. When asserted LOW, the SDO/SDO output driver is powered
off. SDO/SDO will float to V
CC
through the pull-up resistor.
4.3 Output Return Loss Measurement
To perform a practical return loss measurement, it is necessary to force the
GS9077 output to a DC high or low condition. The actual measured return loss will
be based on the outputs being static at V
CC
or V
CC
-1.6V. Under normal operating
conditions the outputs of the device swing between V
CC
-0.4V and V
CC
-1.2V.
44619 - 0
May 2007
9 of 14
GENNUM [ GENNUM CORPORATION ]
