GX4002 Datasheet, PDF (55/74 Pages) Gennum Corporation – Dynamic on-chip power management control

5. Layout Considerations
The following high-frequency design rules should be considered to achieve optimum
performance of the GX4002:
• Use carefully designed controlled-impedance transmission lines with minimal local
discontinuities for all high-speed data signals
• Place decoupling capacitors as close as possible to the supply pins
• For optimal electrical and thermal performance, the QFN’S exposed pad should be
soldered to the module ground plane
• It is recommended to have LF cap ground and VCO caps ground to be common with
multiple stitching of vias to ground. Capacitors should be placed from smallest
value to largest value away from chip
• All supply decoupling capacitors should have multiple vias to ground/power
planes, and placed as close to chip as possible
• All supplies/grounds should be routed to corresponding decoupling capacitors
pads, and never to the centre pad
• The recommended PCB layout for the GX4002 device is shown in Section 7.2
• Some sample layouts are shown in Figure 5-1
SDO0VCC
SDO0VEE
NC
NC
RS1
SDI1
SDI1
Ch1LOS
32 31 30 29 28 27 26 25
1
24
2
23
3
22
4
21
XPOINT
5
20
6
19
7
18
8
9
17
10 11 12 13 14 15 16
GND
Ch0LF
Ch0VCOVEE
Ch0VCOFILT
SDI0
SDI0
Ch0VEE
Ch0VCC
Ground Pad
(bottom of package)
OUT
IN
OUT
GX4002
IN
OUT
GX4002
IN
Figure 5-1: Sample Layouts
OUT
IN
GX4002 2x2 14.025Gb/s Crosspoint Switch with Trace
Equalization and Output De-Emphasis
Data Sheet
55972 - 0
March 2012
55 of 74
Proprietary & Confidential