Skyworks Solutions Inc. SI5345B-B05979-GM

Overview

SI5345B-B05979-GM from Skyworks is a 10-channel, any-frequency jitter attenuator/clock multiplier with fourth-generation DSPLL™ and MultiSynth™ architecture. It delivers ultra-low 90 fs rms jitter, supports differential input frequencies up to 750 MHz and differential outputs up to 1028 MHz, and operates in free-run, locked, or holdover modes - enabling precise clock synthesis for SyncE-compliant 100 GbE line cards.

For engineers reviewing the SI5345B-B05979-GM datasheet, SI5345B-B05979-GM pinout, SI5345B-B05979-GM application, or SI5345B-B05979-GM equivalent, key selection factors include its programmable jitter attenuation bandwidth (0.1 Hz–4 kHz), G.8262 EEC Option 1/2 compliance, 64-QFN 9×9 mm package, I²C/SPI configurability, and factory-programmed NVM configuration for known-power-up behavior.

Technical Context

The SI5345B-B05979-GM implements a fourth-generation DSPLL with fully integrated loop filter and digitally programmable loop bandwidth (0.1 Hz–4 kHz), enabling application-level jitter optimization without external components. Its MultiSynth™ fractional-N synthesis supports hitless switching between fractionally related inputs and glitchless on-the-fly output frequency changes.

It features four configurable inputs (IN0–IN3), ten independently programmable outputs (OUT0–OUT9), and dual-mode reference support (25–54 MHz crystal or external REFCLK). The device includes status monitoring (LOS/OOF/LOL), ramped holdover exit, DCO mode with 0.001 ppb step size, and zero-delay mode with FB_IN on IN3 when enabled.

Key Specifications

Pinout & Package

The SI5345B-B05979-GM is housed in a 64-pin QFN package (9 mm × 9 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined per Skyworks Si5345 Rev D datasheet Section 9 (Pin Descriptions).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar jitter attenuator/clock multiplier applications.

Compared with SI5345A-D-GM, SI5345B-B05979-GM trades maximum output frequency for optimized cost and power in sub-350 MHz SyncE/OTN applications; versus LMK04832RHAR, it provides integrated crystal support and lower jitter but no JESD204B-specific features.

Availability

SI5345B-B05979-GM is available at Aetrix Electronics and suitable for OTN muxponders, 100 GbE Synchronous Ethernet line cards, and broadcast video infrastructure requiring stable component supply, long-term lifecycle assurance, and factory-programmed configuration consistency.

Supply support for SI5345B-B05979-GM 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

Skyworks Solutions is a global semiconductor company specializing in analog and mixed-signal connectivity solutions for communications, industrial, and automotive markets.

The SI5345B-B05979-GM belongs to Skyworks' Si5345 family of jitter-attenuating clock multipliers, designed specifically for high-reliability telecom and datacom infrastructure demanding G.8262 compliance, multi-gigabit SerDes synchronization, and robust holdover performance.

FAQ

What is the primary function of the SI5345B-B05979-GM in a timing architecture?

The SI5345B-B05979-GM serves as a jitter-attenuating clock multiplier that cleans and regenerates noisy input clocks while generating up to ten independent, ultra-low-jitter output frequencies. Its DSPLL architecture locks to input references, suppresses incoming jitter via programmable loop bandwidth, and uses MultiSynth synthesis to deliver precise frequencies required by SerDes, PHYs, and digital signal processors - all within a single 64-QFN package. SI5345B-B05979-GM is preprogrammed to meet specific system timing plans.

Does the SI5345B-B05979-GM support G.8262 Synchronous Ethernet compliance?

Yes, the SI5345B-B05979-GM meets ITU-T G.8262 EEC Option 1 and Option 2 specifications for Synchronous Ethernet equipment clocks. Its 90 fs rms jitter performance, programmable 0.1 Hz–4 kHz jitter attenuation bandwidth, and holdover stability using averaged historical frequency data ensure conformance under both locked and holdover conditions - making SI5345B-B05979-GM suitable for carrier-class Ethernet switches and line cards.

What is the maximum differential output frequency supported by the SI5345B-B05979-GM?

The SI5345B-B05979-GM supports differential output frequencies up to 350 MHz, as indicated by the "B" suffix in its ordering code (per Skyworks Ordering Guide Table 2). This is a factory-configured limitation distinguishing it from the "A" variant (up to 1028 MHz). All 10 outputs (OUT0–OUT9) share this 350 MHz ceiling, and the device retains full fractional synthesis capability within that range. SI5345B-B05979-GM maintains identical jitter, power, and feature sets as higher-frequency variants - only the output frequency ceiling differs.

How is the SI5345B-B05979-GM configured and programmed?

The SI5345B-B05979-GM is configured via I²C or SPI serial interface and stores its configuration in on-chip non-volatile memory (NVM). It powers up with a known, factory-programmed frequency plan - eliminating boot-time configuration overhead. Engineers use Skyworks' ClockBuilder Pro™ software to generate custom configurations, validate jitter performance, and generate programming files. SI5345B-B05979-GM supports in-circuit reprogramming for field updates or prototyping iterations without requiring external programmers.

What reference source does the SI5345B-B05979-GM require for optimal jitter performance?

For optimal jitter performance, the SI5345B-B05979-GM requires a 48–54 MHz fundamental-mode crystal connected to XA/XB pins. Its internal oscillator circuit and integrated load capacitors eliminate need for external caps and reduce noise coupling. While external REFCLK (up to 54 MHz) is supported, crystal-based operation achieves the specified 90 fs rms jitter. In SyncE pizza-box applications requiring ultra-low wander, a TCXO may be substituted - but SI5345B-B05979-GM's default configuration assumes crystal reference.