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MAX4888A/MAX4889A
5.0Gbps PCI Express Passive Switches
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Applications Information
PCIe Switching
The MAX4888A/MAX4889A primary applications are
aimed at reallocating PCIe lanes (see Figure 5). For
example, in graphics applications, several manufacturers
have found that it is possible to improve performance
by a factor of nearly two by splitting a single 16-lane
PCIe bus into two 8-lane buses. Two of the more promi-
nent examples are SLI™ (Scaled Link Interface) and
CrossFire™. The MAX4889A permits a computer
motherboard to operate properly with a single 16-lane
graphics card, and can later be updated to dual cards.
The same motherboard can be used with dual cards
where the user sets a jumper or a bit through software
to switch between single- or dual-card operation.
Common mode below 1V operation requirement.
Board Layout
High-speed switches require proper layout and design
procedures for optimum performance. Keep design-
controlled impedance PCB traces as short as possible
or follow impedance layouts per the PCIe specification.
Ensure that power-supply bypass capacitors are
placed as close to the device as possible. Multiple
bypass capacitors are recommended. Connect all
grounds and the exposed pad to large ground planes.
Common mode below 1V operation requirement.
MAX4888A
MAX4889A
ONE LANE
DATA
DIRECTION
DATA IS ROUTED
TO EITHER
BOARD A OR B
NOTE: ONLY ONE LANE IS SHOWN FOR CLARITY
AB
Figure 5. The MAX4888A/MAX4889A Used as a Single-Lane
Switch
CrossFire is a trademark of ATI Technologies, Inc.
SLI is a trademark of NVIDIA Corporation.
Chip Information
PROCESS: CMOS