Skyworks Solutions Inc. SI5381A-E-GMR

Overview

SI5381A-E-GMR from Skyworks Solutions is a quad-DSPLL ultra-low-jitter wireless jitter attenuator and clock multiplier, designed for BBU/DU timing in 4G/5G wireless infrastructure. It delivers 72 fs RMS jitter (12 kHz–20 MHz), supports CPRI up to 2.94912 GHz via DSPLL_B, Ethernet/general-purpose clocks up to 735 MHz via DSPLL_A/C/D, and operates across –40 to +85 °C with 1.8 V core and 3.3 V analog supply.

For engineers reviewing the SI5381A-E-GMR datasheet, SI5381A-E-GMR pinout, SI5381A-E-GMR application, or SI5381A-E-GMR equivalent, key selection considerations include CPRI/JESD204B clocking capability, hitless/ramped input switching, holdover stability with 54 MHz XO reference, and ITU-T G.8262 compliance for telecom timing.

Technical Context

The SI5381A-E-GMR integrates four independent all-digital DSPLLs: DSPLL_B optimized for high-frequency CPRI clock generation (up to 2.94912 GHz), while DSPLL_A/C/D handle Ethernet, processor, and general-purpose clocks (up to 735 MHz). Its crosspoint architecture enables any input (IN0–IN3) to route to any DSPLL, and any DSPLL output to drive any of 12 configurable outputs.

It features programmable loop bandwidth (20 Hz–4 kHz for DSPLL_B; 1 Hz–4 kHz for DSPLL_A/C/D), Fastlock acquisition mode, automatic hitless/ramped/glitchless input switching, and holdover with 120-second frequency history averaging. The device uses a fixed 54 MHz crystal oscillator (XA/XB) for VCO reference and supports I²C/SPI configuration with on-chip OTP memory.

Key Specifications

Pinout & Package

SI5381A-E-GMR is housed in a 64-pin, 9×9 mm QFN package with exposed thermal pad (RoHS-6 compliant). Pin functions are defined per Skyworks Rev E 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 Si5382A-E-GMR, SI5381A-E-GMR provides two additional DSPLLs for independent Ethernet clock domains and greater output flexibility; versus LTC6957-3IUF#PBF, it delivers 44 fs lower jitter at CPRI frequencies and built-in telecom compliance - making it the sole fit for 5G fronthaul timing.

Availability

SI5381A-E-GMR is available at Aetrix Electronics and suitable for wireless infrastructure, 5G test equipment, and telecom synchronization systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SI5381A-E-GMR 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 wireless, broadband, automotive, and industrial markets.

The Si5381/82 product line was engineered specifically for wireless infrastructure timing - integrating multi-DSPLL jitter attenuation, CPRI-optimized synthesis, and telecom-compliant holdover to replace discrete clock trees in 4G/5G base stations.

FAQ

What is the primary timing function of the SI5381A-E-GMR in 5G wireless systems?

The SI5381A-E-GMR serves as a multi-path jitter attenuator and clock multiplier, simultaneously cleaning and distributing CPRI/eCPRI, Ethernet, and JESD204B clocks in BBU/DU/RRH equipment. Its DSPLL_B generates ultra-low-jitter CPRI clocks up to 2.94912 GHz, while DSPLL_A/C/D provide synchronized Ethernet and general-purpose clocks - all from a single 54 MHz XO reference. This replaces multiple discrete timing ICs in SI5381A-E-GMR-based designs.

Does the SI5381A-E-GMR support ITU-T G.8262 compliance, and how is it implemented?

Yes, the SI5381A-E-GMR is fully compliant with ITU-T G.8262 (EEC Option 1/2) for synchronous equipment clocks. Compliance is achieved through its all-digital DSPLL architecture, 54 MHz XO reference stability, programmable holdover with 120-second frequency history, and robust fault monitoring (LOS/OOF/LOL). These features ensure the SI5381A-E-GMR meets wander and jitter transfer specifications required for telecom synchronization networks without external compensation.

Can the SI5381A-E-GMR generate both device clocks and SYSREF signals for JESD204B subclass 1 systems?

Yes, the SI5381A-E-GMR natively supports JESD204B Subclass 1 by generating both high-stability device clocks (DCLK) and periodic, glitch-free SYSREF signals from the same DSPLL engine. Using independent R-dividers per output, it can configure one output as DCLK (e.g., 307.2 MHz) and another as SYSREF (e.g., 3.84 MHz) with precise phase relationship - all programmable via ClockBuilder Pro. This capability is validated in SI5381A-E-GMR reference designs for multi-converter FPGA systems.

What is the role of the 54 MHz crystal oscillator (XA/XB) in the SI5381A-E-GMR timing architecture?

The 54 MHz crystal oscillator connected to XA/XB serves as the fundamental VCO reference for all four DSPLLs in the SI5381A-E-GMR. It enables free-run and holdover modes, determines long-term frequency stability (<±50 ppm), and directly impacts phase noise performance - especially critical below 1 kHz offset. Skyworks specifies exact XO part numbers for optimal SI5381A-E-GMR jitter; using non-compliant crystals degrades RMS jitter and violates G.8262 holdover specs.

How does the SI5381A-E-GMR handle clock input failures in a redundant wireless timing system?

Upon input failure, the SI5381A-E-GMR automatically transitions from Locked Mode to Holdover Mode using stored frequency history (up to 120 seconds), then to VCO Freeze Mode if holdover history is invalid. It supports hitless, ramped, and glitchless switching between inputs - ensuring continuous, phase-continuous clock output during switchover. Status flags (INTRb) and register bits report LOS/OOF/LOL events in real time, enabling system-level fault response in SI5381A-E-GMR deployments.