Skyworks Solutions Inc. SI5345A-B05985-GM

Overview

SI5345A-B05985-GM from Skyworks is a 10-channel, any-frequency jitter attenuator/clock multiplier featuring fourth-generation DSPLL™ and MultiSynth™ architectures. It delivers ultra-low 90 fs rms jitter, supports differential inputs up to 750 MHz and outputs up to 1028 MHz, and operates in free-run, locked, or holdover modes - deployed in OTN transponders and SyncE-compliant carrier Ethernet switches.

For engineers reviewing the SI5345A-B05985-GM datasheet, SI5345A-B05985-GM pinout, SI5345A-B05985-GM application, or SI5345A-B05985-GM equivalent, key selection considerations include its G.8262 EEC Option 1/2 compliance, programmable jitter attenuation bandwidth (0.1 Hz–4 kHz), 64-QFN 9×9 mm package, I²C/SPI configurability, and factory preprogrammed NVM configuration for known-power-up frequency behavior.

Technical Context

The SI5345A-B05985-GM implements a digitally controlled DSPLL with fractional input dividers (P) enabling hitless switching between fractionally related input clocks, and high-resolution MultiSynth output dividers (N) supporting integer/fractional synthesis. Its loop filter is fully integrated on-chip, eliminating external passive components and associated noise coupling risks.

It features programmable jitter attenuation bandwidth (0.1 Hz–4 kHz), Fastlock mode for accelerated lock acquisition, DCO mode with 0.001 ppb step size, and synchronized ramped holdover exit using user-defined ramp rates (0.2–40,000 ppm/s). Status monitoring includes LOS, OOF, and LOL flags with interrupt pin (INTRb) support.

Key Specifications

Pinout & Package

The SI5345A-B05985-GM is housed in a 64-pin QFN package (9×9 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 applications.

Compared with SI5345A-B05985-GM, Si5345B-D-GM trades output frequency range and synthesis flexibility for lower unit cost, while LTC6955IUF#PBF offers superior raw jitter performance but lacks telecom-grade holdover, programmable bandwidth, and multi-output configurability - making SI5345A-B05985-GM uniquely suited for field-deployable SyncE and OTN timing systems.

Availability

SI5345A-B05985-GM is available at Aetrix Electronics and suitable for OTN transponders, SyncE carrier switches, broadcast video infrastructure, and test equipment requiring stable component supply, guaranteed long-term lifecycle support, and factory-programmed configuration consistency.

Supply support for SI5345A-B05985-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, automotive, and industrial markets.

The SI5345A-B05985-GM belongs to Skyworks' Si5345 family of jitter-attenuating clock multipliers, designed specifically for high-reliability telecom infrastructure demanding G.8262 compliance, seamless holdover, and multi-protocol timing flexibility.

FAQ

What is the primary function of the SI5345A-B05985-GM in a telecom timing system?

The SI5345A-B05985-GM serves as a jitter-attenuating clock multiplier that cleans and regenerates timing signals from noisy or unstable sources while generating multiple synchronized, low-jitter output clocks. In telecom systems, it enables compliance with ITU-T G.8262 EEC Option 1/2 by reducing input jitter to <90 fs rms and maintaining stable holdover timing during input failures - a core requirement in OTN and SyncE deployments where SI5345A-B05985-GM is commonly used.

Does the SI5345A-B05985-GM require an external crystal, and what frequency range is supported?

Yes, the SI5345A-B05985-GM requires an external crystal connected to the XA/XB pins for stable free-run and holdover operation. It supports crystals from 25 MHz to 54 MHz, with Skyworks recommending 48–54 MHz for optimal jitter performance. The device integrates internal load capacitors, eliminating the need for external CL components - a design feature confirmed in the Si5345 Rev D datasheet Section 3.5 and Table 5.12, ensuring SI5345A-B05985-GM achieves its specified 90 fs rms jitter.

How does the SI5345A-B05985-GM handle input clock failures in a redundant timing architecture?

Upon input clock failure, the SI5345A-B05985-GM automatically enters holdover mode using up to 120 seconds of stored historical frequency data to compute a stable averaged holdover frequency. This value is derived from a programmable time window and delay to exclude corrupted pre-failure samples. The DSPLL then pulls output frequency to this holdover value with glitchless ramping - a behavior documented in Section 3.4.5 of the Si5345 Rev D datasheet and essential for maintaining SI5345A-B05985-GM reliability in carrier-grade SyncE systems.

Can the SI5345A-B05985-GM generate different output frequencies simultaneously, and how is this configured?

Yes, the SI5345A-B05985-GM can generate up to 10 independent output frequencies simultaneously, each programmable via its own MultiSynth divider chain. Configuration is performed using Skyworks' ClockBuilder Pro™ software, which calculates exact P/N/R divider values for any input-to-output frequency mapping - including integer and fractional synthesis. These settings are stored in on-chip NVM, ensuring SI5345A-B05985-GM powers up with the intended frequency plan without host intervention.

Is the SI5345A-B05985-GM pin-compatible with other devices in the Si5345 family, such as the Si5345B-D-GM?

No, the SI5345A-B05985-GM is not pin-compatible with Si5345B-D-GM. While both share the same 64-QFN 9×9 mm package footprint and pinout definition per Skyworks' Si5345 Rev D datasheet Section 10.1, SI5345A-B05985-GM is a factory preprogrammed variant with a unique configuration encoded in its part number suffix (B05985), whereas Si5345B-D-GM is a blank, unprogrammed version requiring post-manufacture configuration. Their functional compatibility depends on programmed settings, not mechanical interchangeability.