Microchip Technology VSC8256EV

Overview

VSC8256EV from Microsemi is a quad-channel, protocol-agnostic 1G/10G serial-to-serial repeater/retimer with integrated host-side 10GBASE-KR auto-negotiation and training. It supports 10.3125 Gbps LAN, 9.95328 Gbps WAN, and 1.25 Gbps modes across four bidirectional lanes, operates on 1.2 V/1.0 V core supplies, delivers <0.5 UI peak-to-peak output jitter, and targets backplane signal integrity in 10GbE line cards and NICs.

For engineers reviewing the VSC8256EV datasheet, VSC8256EV pinout, VSC8256EV application, or VSC8256EV equivalent, key selection considerations include KR-compliant backplane retiming, SFP+/QSFP+ line module interfacing, SyncE clocking support, and hardware-based host-side training for 10GBASE-KR links.

Technical Context

The VSC8256EV implements four independent SD10G retimer channels with adaptive equalization on receive and programmable multi-tap pre-emphasis on transmit. Each channel includes an elastic buffer and LCPLL-based clock recovery supporting both LAN and WAN data rates using a single 156.25 MHz reference clock.

It integrates SPI, MDIO, and two-wire serial (TWS) slave interfaces for configuration and monitoring, plus built-in self-test (BIST), line/client loopbacks, and pattern generation. SyncE compliance per ITU-T G.8262 is enabled via its flexible clocking network.

Key Specifications

Pinout & Package

Package: 196-ball Fine-Pitch Chip Array Ball Grid Array (FCBGA), 12 mm × 12 mm, 0.8 mm pitch, RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 1G/10G serial retimer applications.

Compared with VSC8256EV, the 88X3310 requires external training control and offers no SyncE or BIST, while the LAN8870 omits WAN mode and KR auto-negotiation-making VSC8256EV uniquely suited for carrier-grade, multi-lane KR backplane systems requiring autonomous training and telecom timing.

Availability

VSC8256EV is available at Aetrix Electronics and suitable for 10GBASE-KR backplane transceivers, multi-port SFP+/QSFP+ line cards, and rack-mount server LOM designs requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for VSC8256EV 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 analog, mixed-signal, and timing ICs for communications, aerospace, defense, and industrial markets.

The VSC8256EV belongs to Microsemi's Ethernet Signal Integrity product line, engineered specifically for KR-compliant backplane retiming, SFP+/QSFP+ interconnection, and SyncE-enabled telecom infrastructure.

FAQ

What is the primary function of the VSC8256EV in a 10GBASE-KR backplane system?

The VSC8256EV acts as a quad-channel serial-to-serial repeater/retimer that cleans jitter, compensates for channel loss, and performs hardware-based host-side 10GBASE-KR auto-negotiation and training. In a backplane system, it ensures robust 10G link establishment between line cards and switch fabrics without host CPU involvement-critical for carrier-grade reliability. The VSC8256EV achieves this using adaptive equalization and programmable pre-emphasis on each of its four independent SD10G lanes.

Does the VSC8256EV support both LAN and WAN data rates, and how is this implemented?

Yes, the VSC8256EV supports 10.3125 Gbps (LAN) and 9.95328 Gbps (WAN) modes, plus 1.25 Gbps. This is implemented via configurable LCPLLs synchronized to a single 156.25 MHz reference clock-eliminating need for multiple clock sources. The device's retiming architecture adapts to each rate without reconfiguration, enabling seamless interoperability across enterprise and telecom infrastructure. The VSC8256EV maintains jitter performance <0.5 UI pk-pk across all supported rates.

How does the VSC8256EV handle clocking for Synchronous Ethernet (SyncE) applications?

The VSC8256EV integrates a clocking network compliant with ITU-T G.8262 EEC Option 1/2, supporting SyncE phase alignment and holdover. Its LCPLLs lock to the 156.25 MHz reference while maintaining sub-50 ns phase error under variable packet delay-meeting metro edge timing requirements. The VSC8256EV does not generate SyncE clocks itself but recovers and distributes them with telecom-grade stability, enabling timing-aware backplane designs without external timing ICs.

Can the VSC8256EV be used with passive copper cables, and what is the maximum validated length?

Yes, the VSC8256EV is validated for use with passive direct-attach copper (DAC) cables up to 3 meters at 10.3125 Gbps. Its programmable multi-tap transmitter pre-emphasis and adaptive receiver equalization compensate for insertion loss and reflections in low-cost copper assemblies. This capability allows system designers to avoid expensive active optical modules in top-of-rack and intra-rack interconnects-while maintaining full IEEE 802.3 compliance. The VSC8256EV's signal conditioning ensures BER <10⁻¹² over the full 3 m range.

What management interfaces does the VSC8256EV provide, and how are they used in system integration?

The VSC8256EV provides SPI, MDIO, and two-wire serial (TWS) slave interfaces for configuration and monitoring. SPI is used for fast initialization and per-channel retimer tuning (equalization, pre-emphasis, BIST); MDIO enables IEEE 802.3-compliant register access for link status and KR AN state; TWS supports lightweight telemetry in space-constrained designs. All interfaces operate concurrently-allowing host firmware to configure KR training parameters, read error counters, and trigger loopbacks without interrupting traffic. The VSC8256EV's dual-interface flexibility simplifies integration across switch ASICs, BMCs, and FPGA-based controllers.