Microchip Technology VSC8491YJU-13

Overview

VSC8491YJU-13 from Microsemi is a dual-channel 10G/1G SerDes PHY IC supporting IEEE 1588v2 timing with ≤4 ns accuracy at 1.25 Gbps and 10.3 Gbps, 128/256-bit MACsec (IEEE 802.1AE), and full 10GBASE-KR (IEEE 802.3ap) compliance. It integrates RXAUI/XAUI to SFP+/KR conversion, VeriTime™ precision timing, and hardware-based KR state machine for carrier-grade Ethernet line cards and secure interconnects.

For engineers reviewing the VSC8491YJU-13 datasheet, VSC8491YJU-13 pinout, VSC8491YJU-13 application, or VSC8491YJU-13 equivalent, key selection criteria include IEEE 1588v2 sub-4 ns timestamping accuracy, MACsec encryption/decryption capability, KR autonegotiation support, SFP+ host interface compliance per SFF-8431, and dual-rate (1.25/10.3 Gbps) SerDes operation in a single 13 mm × 13 mm QFN package.

Technical Context

The VSC8491YJU-13 implements a dual-lane SerDes architecture with independent RXAUI/XAUI client interfaces and SFP+/KR line interfaces, each supporting 1.25 Gbps WAN, 10.3 Gbps LAN, and 10GBASE-KR backplane operation. Its integrated VeriTime™ engine delivers hardware-accelerated PTP timestamping with 1-step and 2-step frame handling for ordinary, boundary, and transparent clock modes.

It embeds a full MACsec engine compliant with IEEE 802.1AE for frame encryption/decryption, input classification, and latency-aware performance monitoring, alongside Y.1731 OAM for real-time link health assessment. Clocking supports Synchronous Ethernet via single 156.25 MHz reference input and includes failover switching, lane ordering, and adaptive equalization with programmable multitap transmitter pre-emphasis.

Key Specifications

Pinout & Package

The VSC8491YJU-13 is housed in a 128-pin 13 mm × 13 mm QFN package with exposed thermal pad, optimized for high-speed signal integrity and thermal dissipation in carrier Ethernet applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar SerDes PHY applications.

Compared with the Marvell 88X3310 and Intel X710-AT2, the VSC8491YJU-13 uniquely combines hardware-accelerated IEEE 1588v2 timing, MACsec offload, and dual-mode (RXAUI/XAUI + SFP+/KR) SerDes in one device - making it the only choice for carrier-grade timing-aware line cards requiring both security and backplane interoperability.

Availability

VSC8491YJU-13 is available at Aetrix Electronics and suitable for carrier Ethernet line cards, secure data center interconnects, and 10GBASE-KR backplane transceivers requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for VSC8491YJU-13 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

Microsemi Corporation (now part of Microchip Technology) designs high-reliability semiconductor solutions for communications, aerospace, defense, and industrial markets, with emphasis on timing, security, and signal integrity.

The VSC8491YJU-13 belongs to Microsemi's VeriTime™-enabled Ethernet PHY product line, engineered specifically for carrier-class timing-critical infrastructure where sub-4 ns IEEE 1588v2 accuracy, MACsec encryption, and KR backplane reliability are mandatory.

FAQ

What is the IEEE 1588v2 timing accuracy of the VSC8491YJU-13?

The VSC8491YJU-13 achieves ≤4 ns IEEE 1588v2 timestamping accuracy at both 1.25 Gbps and 10.3 Gbps data rates using its dedicated VeriTime™ hardware engine. This precision is measured under standard operating conditions and enables compliance with ITU-T G.8275.1 PRTC requirements. The VSC8491YJU-13 does not rely on software timestamping, eliminating stack-induced jitter that degrades timing fidelity in boundary clock applications.

Does the VSC8491YJU-13 support both 1-step and 2-step PTP frames?

Yes, the VSC8491YJU-13 fully supports both 1-step and 2-step Precision Time Protocol (PTP) frames for ordinary clock, boundary clock, and transparent clock configurations per IEEE 1588v2. Its hardware timestamping engine inserts correction fields directly into PTP messages without CPU intervention. This capability is integral to the VSC8491YJU-13's role in carrier Ethernet timing distribution and ensures deterministic latency in time-sensitive networking deployments.

What MACsec key lengths does the VSC8491YJU-13 support?

The VSC8491YJU-13 supports both 128-bit and 256-bit AES encryption keys per IEEE 802.1AE (MACsec) specifications. Key management is handled via MDIO or SPI interface, allowing dynamic session key rotation without interrupting data flow. This dual-key-length capability makes the VSC8491YJU-13 suitable for environments with varying security policy requirements, including government and financial sector interconnects where 256-bit keys are mandated.

Is the VSC8491YJU-13 compatible with SFP+ SR/LR optical modules?

Yes, the VSC8491YJU-13 meets all SFP+ host electrical requirements defined in SFF-8431, including SR, LR, ER, ZR, and 220MMF variants. It provides adaptive equalization and transmitter pre-emphasis to compensate for optical impairments and PCB trace degradation. This ensures robust link establishment and bit-error-rate performance with commercial SFP+ modules, making the VSC8491YJU-13 ideal for pluggable-optics-based NICs and line cards.

What clocking options does the VSC8491YJU-13 support for Synchronous Ethernet?

The VSC8491YJU-13 supports Synchronous Ethernet via a single 156.25 MHz differential reference clock input (REFCLK_P/N), enabling seamless Layer 1 frequency synchronization across WAN/LAN domains. Its internal PLL network distributes recovered clocks with low jitter to all SerDes lanes and timing blocks. This clocking architecture allows the VSC8491YJU-13 to serve as a SyncE-compliant timing source in edge routers and aggregation switches without external clock synthesizers.