Analog Devices Inc./Maxim Integrated VSC7173XYI

Overview

VSC7173XYI from Maxim Integrated is a Serial ATA and Serial Attached SCSI 2:1 port selector / 1:2 port multiplier IC supporting 1.5 Gbps and 3.0 Gbps links, featuring programmable receiver sensitivity, high-output swing with pre-emphasis, and LVTTL-configurable operation modes for redundant storage subsystems.

For engineers reviewing the VSC7173XYI datasheet, VSC7173XYI pinout, VSC7173XYI application, or VSC7173XYI equivalent, this device enables dual-host failover to single-port SATA/SAS drives, supports transparent OOB signal transfer during port switching, and delivers configurable output amplitude for backplane and external cable drive.

Technical Context

The VSC7173XYI implements dual operational modes-level- or edge-sensitive port selection-controlled by MODE1, PORTSEL0, and PORTSEL1 pins, with MODE0 determining unselected port behavior (off or data replication). Its architecture includes three independent high-speed differential ports (P0, P1, P2) with AC-coupled I/O and dedicated OOB detectors per input.

Each port's output buffer supports two swing levels (normal: 500–700 mV_p-p; high: 800–1300 mV_p-p) and pre-emphasis when HIVx = HIGH, while OOB threshold is globally set via OOBSEL[1:0] to nominal (150–250 mV), ±40 mV, or −80 mV differential peak-to-peak.

Key Specifications

Pinout & Package

The VSC7173XYI is housed in a 32-pin leadless quad flat pack (QFP-N) with 7 mm × 7 mm body, 0.9 mm height, and an exposed die attach pad (DAP) internally connected to ground and requiring board-level connection to VSS.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SATA/SAS port selection and multiplication applications.

Compared with VSC7175 and VSC7177, the VSC7173XYI provides the essential 2:1/1:2 switching functionality at lowest BOM cost and power (625 mW), with no unnecessary features for SATA-centric storage subsystems requiring proven 3.0 Gbps reliability.

Availability

VSC7173XYI is available at Aetrix Electronics and suitable for active-passive failover systems, SATA port replicators, and dual-host disk arrays requiring stable component supply, long-lifecycle support, and lead(Pb)-free compliance.

Supply support for VSC7173XYI includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Maxim Integrated is a U.S.-based semiconductor company specializing in analog and mixed-signal ICs for industrial, communications, and computing applications.

The VSC7173XYI belongs to Maxim's serial interface and storage connectivity product line, designed specifically to simplify high-availability SATA/SAS subsystem architecture while maintaining strict protocol transparency and signal integrity.

FAQ

What is the primary function of the VSC7173XYI in a storage system?

The VSC7173XYI serves as a dual-function Serial ATA and Serial Attached SCSI interface IC that operates either as a 2:1 port selector (enabling two hosts to share one drive) or a 1:2 port multiplier (allowing one host to connect two drives). Its design ensures transparent OOB signal handling and maintains SATA 1.0 compliance at 1.5 Gbps while supporting 3.0 Gbps operation. The VSC7173XYI is used in high-availability storage subsystems where redundancy, load sharing, and signal integrity across backplanes or cables are critical.

Does the VSC7173XYI require external configuration components to operate?

No, the VSC7173XYI uses LVTTL-level control pins (PORTSEL0, PORTSEL1, MODE0, MODE1, HIVx, OOBSEL[1:0]) for mode selection and signal conditioning-no external EEPROM, resistors, or clocks are needed. All configuration is done via hardwired logic levels or GPIO from a host controller. AC-coupling capacitors (0.01 μF recommended) are required on all high-speed differential I/O lines, but these are standard signal integrity components, not configuration elements. The VSC7173XYI powers up in a defined state based on PORTSEL0/PORTSEL1 levels.

Can the VSC7173XYI support both SATA and SAS protocols simultaneously?

Yes, the VSC7173XYI is explicitly designed to handle both Serial ATA and Serial Attached SCSI links in identical electrical and functional modes. It passes SATA patterns transparently, supports SAS-compatible 1.5/3.0 Gbps data rates, and preserves out-of-band signaling required by both protocols during port switching. However, it does not perform protocol translation-each connected device must use the same protocol as its host; mixed SATA/SAS endpoints on the same VSC7173XYI are not supported.

What thermal considerations apply to the VSC7173XYI in continuous operation?

The VSC7173XYI has a junction-to-ambient thermal resistance (θ_JA) of 30.0°C/W at 0 ft/min airflow, dropping to 27.0°C/W at 200 ft/min. With typical power dissipation of 625 mW (normal swing) or 850 mW (high swing), junction temperature rise can reach 18.8°C or 22.9°C above ambient under still-air conditions. To maintain operation within the +90°C max case temperature limit, the exposed die attach pad (DAP) must be soldered to a minimum 100 mm² copper pour connected to VSS, and airflow ≥100 ft/min is recommended for sustained high-swing mode use.

How does the VSC7173XYI handle port switching latency and link reinitialization?

The VSC7173XYI guarantees a maximum port switch time (t_SW) of 5.0 ns after an active edge on PORTSEL0 or PORTSEL1, but full SATA link reinitialization-including OOB signaling-requires additional time governed by the SATA specification (typically ~10 ms). The VSC7173XYI transparently forwards all OOB sequences (COMRESET, etc.) between hosts and drive without modification or delay, ensuring standard SATA link training completes successfully. No special firmware or timing adjustments are needed beyond adhering to the 4 ns minimum pulse width (t_PW) and 5 ns separation (t_PSS) on selection pins.