GENERAL DESCRIPTION
The VSC7173 is a Serial ATA and Serial Attached SCSI multiplexer and buffer that implements a 2:1 port selector function for 1.5 Gbps and 3.0 Gbps links. This function is used when dual hosts, such as I/O controllers, must access single-port disk drives in high availability storage subsystems where redundancy and load sharing are important. The outputs from the I/O controllers are multiplexed to a Serial ATA or Serial Attached SCSI drive. The output from the Serial ATA drive is buffered and replicated to the I/O controllers. When switching from one I/O controller to the other, a Serial ATA link must be re-initialized with out-of-band (OOB) signals, which are transferred through the VSC7173 transparently. The VSC7173 provides high output swings with pre-emphasis, and programmable receiver sensitivity that are needed to drive long backplanes and external cables.
In addition to the above features, the VSC7173 also supports a 1:2 port multiplier mode where one host can connect two drives.

FEATURES
● 2:1 port selector and 1:2 port multiplier for both Serial ATA (SATA) and Serial Attached SCSI (SAS) links
● Serial ATA 1.0 compliant at 1.5 Gbps (3.0 Gbps capable)
● Passes Serial ATA patterns transparently
● Programmable receiver sensitivity
● High output swing mode with pre-emphasis
● Compatible with VSC7175 and VSC7177 designs
● 0.7 W power dissipation
● 3.3 V power supply
● 32-pin, 7 mm x 7 mm QFP-N package

APPLICATIONS
● Active-passive redundant failover systems
● Dual-port Serial ATA and Serial Attached SCSI disk arrays (JBODs)
● NAS servers
● RAID subsystems
● Disk-based backup systems
● Serial ATA and Serial Attached SCSI routing applications
● Buffers for externally connected links
● Serial ATA port replicators
● Serial ATA Host Bus Adapters selecting between internal and external connectors