EB-GS2985-S
Evaluation Board User Guide
52246 - 2
July 2009
9 of 25
1.7 Power Pins
The default supply configuration allows for quick power-up of the EB-GS2985-S by
applying 3.3V to the EQ post and grounding the GND post. Power supply connections
can be changed to evaluate each device seperately over their specified range of supply
voltages.
The GS2984 EQ accepts a 3.3V power supply, while the GS2985 RCLK and GS2988 CD
accept either 3.3V or 2.5V. Furthermore, the termination voltage (CD_TERM) on the
GS2988 CD accepts up to 5V when a high output swing is desired.
Please refer to
Figure 1-2
. The EB-GS2985-S evaluation board uses an external power
supply through a power post labelled “EQ” to power the EQ at 3.3V. Optionally, a second
power supply can be connected to the post labelled “RCLK” to power the GS2985 and a
third power supply can be connected to the post labelled “CD” to power-up the GS2988
device. Alternatively, the “RCLK” supply can track the “EQ” supply by properly
configuring the RCLK_SEL jumper. Similarly, the “CD” supply can track the “RCLK”
supply by properly configuring the CD_SEL jumper. By default, the jumpers are
configured so that all three devices are powered off the same supply connected to the
“EQ” post. The power supply configuration jumpers are described in
Table 1-9
,
Table 1-10
and
Table 1-11
.
NOTE: The cable driver power supply (CD) cannot have a higher potential than the
reclocker power supply (RCLK).
Table 1-8: RSET Resistor Select (RSET_SEL)
Label
Connection
Description
R19 (default)
800mV output swing
R20
1.8V output swing
NOTE: The CD_TERM post
should be connected to 5V,
and the CD_TERM_SEL
jumper should be set to EXT
in order to achieve this
output swing.
R21
500mV output swing
