GS1528 Gennum Corporation, GS1528 Datasheet - Page 5

• Manufacturer Part Number: GS1528
• Description: Multi-rate Dual Slew-rate Cable Driver For HD-SDI, Sd-sdi & DVB-ASI. 3.3V Supply.
• Manufacturer: Gennum Corporation

OUTPUT RETURN LOSS MEASUREMENT
To perform a practical return loss measurement, it is
necessary to force the GS1528 output to a DC high or low
condition. The actual measured return loss will be based on
the outputs being static at V
operating conditions the outputs of the GS1528 swing
between V
return loss will not represent the actual operating return
loss.
A simple method of calculating the values of actual
operating return loss is to interpolate the two return loss
measurements. In this way, the values of return loss are
estimated at V
measurements at V
The two values of return loss (high and low) will typically
differ by several decibels. If the measured return loss is R
for logic high and R
be interpolated as follows:
where R
interpolated logic low value.
For example, if R
interpolated values are R
OUTPUT AMPLITUDE ADJUSTMENT
The output amplitude of the GS1528 can be adjusted by
changing the value of the R
and Table 1. For an 800mV
tolerance, a value of 750Ω is required. A ±1% SMT resistor
should be used.
GENNUM CORPORATION
R
R
IH
IH
IL
= R
is the interpolated logic high value and R
CC
= R
-0.4V and V
L
H
+(R
- (R
Fig. 6 Static Protection Diodes
CC
H
H
H
CC
-0.4V and V
-R
L
-R
= -18dB and R
GS1528
for logic low, then the two values can
and V
L
L
)/4
)/4 and
IH
CC
= -17dB and R
-1.2V, so the measured value of
SET
CC
p-p
CC
-1.6V.
resistor as shown in Figure 7
output with a nominal ±7%
or V
CC
-1.2V based on the
CC
L
-1.6V. Under normal
= -14dB, then the
IL
SDO
SDO
= -15dB.
IL
is the
H
5
The R
the GS1528. The resistor should be placed as close as
possible to the R
should be minimized at this node by removing the PCB
groundplane beneath the R
NOTE: For reliable operation of the GS1528 over the full
temperature range, do not use an R
TABLE 1: R
SET
1100
1000
900
800
700
600
resistor is part of the high speed output circuit of
500
R
SET
SET
995
824
750
600
573
Fig. 7 Output Amplitude Adjustment
vs V
R (Ω)
SET
OD
600
pin. In addition, the PCB capacitance
R
SET
700
SET
R (Ω)
resistor and the R
SET
800
OUTPUT SWING
value below 573Ω.
1040
608
734
800
884
900
SET
pin.
16632 - 2
1000