Skyworks Solutions Inc. SI5324B-C-GMR

Overview

SI5324B-C-GMR from Skyworks Solutions is a low-bandwidth jitter-attenuating clock multiplier IC based on 3rd-generation DSPLL® technology. It accepts two differential input clocks (2 kHz–710 MHz), generates two independent output clocks (2 kHz–945 MHz, up to 1.4 GHz at select ratios), and delivers ultra-low jitter of 290 fs rms (12 kHz–20 MHz). It operates from single 1.8/2.5/3.3 V supply and supports LVPECL/LVDS/CML/CMOS output formats - deployed in Synchronous Ethernet line cards and OTN demapping systems.

For engineers reviewing the SI5324B-C-GMR datasheet, SI5324B-C-GMR pinout, SI5324B-C-GMR application, or SI5324B-C-GMR equivalent, key selection considerations include programmable loop bandwidth (4–525 Hz), hitless clock switching with <200 ps phase step, compliance with ITU-T G.8251 and GR-253-CORE jitter specs, and I²C/SPI configurability for frequency synthesis across telecom and broadcast timing systems.

Technical Context

The SI5324B-C-GMR implements a digitally controlled DSPLL architecture with dual independent input clock paths (CKIN1/CKIN2), each supporting loss-of-signal detection and automatic/fallback switching. Its core PLL uses an external crystal or reference clock (XA/XB) as the stability anchor, enabling precise jitter attenuation while synthesizing arbitrary output frequencies via high-resolution N-divider chains.

It integrates on-chip voltage regulation with high PSRR, configurable signal format per output, and alarm outputs (LOL, LOS, FOS) for real-time monitoring. The device supports digital hold mode with historical frequency averaging and freerun operation - critical for maintaining timing continuity during reference loss in carrier-grade infrastructure.

Key Specifications

Pinout & Package

SI5324B-C-GMR is housed in a 6 × 6 mm, 36-pin QFN package with exposed thermal pad. Pin assignments are validated per Skyworks Rev. 1.1 datasheet (pages 2–3, 60–63).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar jitter-attenuating clock multiplier applications.

Compared with Si5325B-C-GM and LMK04828BISQE/NOPB, SI5324B-C-GMR provides optimal balance of jitter performance (290 fs), integration (no external VCXO/filter), and footprint (6×6 mm) for telecom timing - making it the preferred choice for cost- and space-constrained SyncE and OTN line cards.

Availability

SI5324B-C-GMR is available at Aetrix Electronics and suitable for Synchronous Ethernet line cards, OTN demapping systems, and broadcast video genlock applications requiring stable component supply, full lifecycle support, and guaranteed traceability.

Supply support for SI5324B-C-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 leader in analog and mixed-signal semiconductors, specializing in RF, timing, and connectivity solutions for infrastructure, automotive, and mobile markets.

The Si5324 family was engineered specifically for carrier-grade timing applications - delivering jitter attenuation, hitless switching, and multi-standard compliance required in telecom, datacom, and broadcast equipment.

FAQ

What is the maximum output frequency supported by the SI5324B-C-GMR?

The SI5324B-C-GMR supports output frequencies up to 945 MHz across its full operating range. At select integer-N configurations (N1 = 4), it achieves up to 1.4 GHz - verified in Table 3 AC Characteristics of the Skyworks Rev. 1.1 datasheet. This capability enables direct generation of OTU-4 line rates and 100G SyncE frequencies without external multiplication.

Does the SI5324B-C-GMR support both I²C and SPI interfaces simultaneously?

No, the SI5324B-C-GMR uses a single serial interface selected at power-up via the CMODE pin: low for I²C, high for SPI. Both protocols are fully supported, but only one is active per configuration. The SI5324B-C-GMR does not allow concurrent use - design must commit to one interface during hardware layout.

How does the SI5324B-C-GMR achieve hitless clock switching?

The SI5324B-C-GMR performs phase build-out on the standby input before switching, aligning output phase edges to within ≤200 ps of the active path. This is implemented in hardware using internal phase interpolators and delay-locked loops - no firmware intervention is required. The SI5324B-C-GMR meets Telcordia GR-253-CORE requirements for seamless failover in carrier networks.

Can the SI5324B-C-GMR operate from a 1.8 V supply while driving LVPECL outputs?

No. Per Table 2 DC Characteristics, LVPECL outputs require nominal VDD ≥2.5 V. When powered from 1.8 V, the SI5324B-C-GMR supports only LVDS, CML, or CMOS output formats. Driving LVPECL at 1.8 V would violate absolute maximum ratings and result in undefined signal integrity - the SI5324B-C-GMR must be supplied with ≥2.5 V for LVPECL operation.

What crystal frequency is recommended for the XA/XB pins of the SI5324B-C-GMR?

Skyworks specifies 114.285 MHz (3rd-overtone) as the reference crystal for XA/XB in typical application circuits (Figures 3 and 4). This frequency optimizes DSPLL loop stability and phase noise performance. The SI5324B-C-GMR also accepts other fundamental or overtone crystals between 10–150 MHz, but 114.285 MHz is the validated and characterized reference for telecom-grade jitter attenuation.