MAX4888/MAX4889
2.5Gbps PCI Express Passive Switches
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Applications Information
PCIe Switching
The MAX4888/MAX4889 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 prominent
examples are SLI™ (Scaled Link Interface) and
CrossFire™. The MAX4889 permits a computer mother-
board to operate properly with a single 16-lane graph-
ics 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.
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.
Figure 5. The MAX4888/MAX4889 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
