Skyworks Solutions Inc. SI5351A-B04691-GTR

Overview

SI5351A-B04691-GTR from Skyworks Solutions is an I²C-programmable, 8-output CMOS clock generator with integrated VCXO, designed to replace crystals, crystal oscillators, and discrete PLLs in cost-sensitive embedded systems. It delivers up to eight independent, non-integer-related frequencies from 2.5 kHz to 200 MHz with 0 ppm synthesis error, operates from a 25/27 MHz crystal, and supports 1.8/2.5/3.3 V output voltage levels for mixed-signal timing in audio/video equipment and networking gear.

For engineers reviewing the SI5351A-B04691-GTR datasheet, SI5351A-B04691-GTR pinout, SI5351A-B04691-GTR application, or SI5351A-B04691-GTR equivalent, this device offers precise multi-domain clock synthesis, programmable rise/fall time control, glitchless frequency changes, and configurable spread spectrum-critical for PCIe Gen 1 compliance, HCSL-compatible swing, and low-jitter system timing.

Technical Context

The SI5351A-B04691-GTR implements a dual-PLL architecture (PLLA + VCXO-based PLLB) feeding eight independent MultiSynth fractional dividers, enabling simultaneous generation of asynchronous and synchronous clocks. Its input stage accepts only a 25 or 27 MHz crystal (no CLKIN or VC pin support), and all outputs derive from PLLA - confirming it is the Si5351A variant without VCXO tuning capability despite "B" in part number suffix.

Each output features separate VDDO supply pins (1.8/2.5/3.3 V), static phase offset control, and programmable drive strength. Output jitter is specified at ≤95 ps pk-pk (period) and ≤90 ps pk (cycle-to-cycle) under full 8-output load, with rise/fall times ≤1.5 ns at 5 pF load - validated for use in high-speed digital interfaces requiring deterministic timing alignment.

Key Specifications

Pinout & Package

SI5351A-B04691-GTR is housed in a 20-pin QFN package (4 mm × 4 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined per Skyworks datasheet Rev. 1.3, Section 10.1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar clock generator applications.

Compared with SI5351A-B04691-GTR, Si5351A-B-GM offers identical functionality but requires host MCU initialization, while Si5351B-B-GM adds VCXO capability for closed-loop timing control - making it suitable for applications demanding tunable output stability beyond fixed-crystal accuracy.

Availability

SI5351A-B04691-GTR is available at Aetrix Electronics and suitable for audio/video equipment, networking/communication devices, and laser range finders requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for SI5351A-B04691-GTR 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, automotive, and industrial markets.

The SI5351A-B04691-GTR belongs to Skyworks' Si5351 family of programmable clock generators, engineered to replace multiple discrete timing components with a single configurable IC for cost-sensitive, space-constrained embedded systems.

FAQ

What is the reference clock requirement for SI5351A-B04691-GTR?

The SI5351A-B04691-GTR requires a 25 MHz or 27 MHz fundamental-mode AT-cut crystal connected to XA/XB pins. It does not accept external clock inputs (CLKIN is NC), nor does it support VCXO tuning (VC is NC). Internal load capacitance is configurable (0/6/8/10 pF), eliminating need for external caps in most cases. SI5351A-B04691-GTR relies solely on this crystal for all timing synthesis.

Does SI5351A-B04691-GTR support spread spectrum clocking?

Yes, SI5351A-B04691-GTR supports per-output spread spectrum clocking with selectable down-spread (–0.1% to –2.5%) or center-spread (±0.1% to ±1.5%) modulation at 31.5 kHz nominal rate. This feature reduces electromagnetic interference in noise-sensitive applications like audio equipment and medical devices without affecting functional timing margins. Configuration is done via I²C register writes to SI5351A-B04691-GTR.

Can SI5351A-B04691-GTR generate PCIe Gen 1 compliant clocks?

Yes, SI5351A-B04691-GTR meets PCIe Gen 1 jitter specifications: period jitter ≤95 ps pk-pk and cycle-to-cycle jitter ≤90 ps pk under full 8-output load. Its low-noise PLL architecture, 0 ppm synthesis error, and configurable output drive strength ensure robust signal integrity at 100 MHz - the standard PCIe Gen 1 reference clock frequency. SI5351A-B04691-GTR has been validated for this use case in networking equipment designs.

What are the power supply requirements for SI5351A-B04691-GTR?

SI5351A-B04691-GTR requires two independent supply domains: VDD core (2.25–2.75 V or 3.0–3.6 V) and four VDDO rails (each 1.71–1.89 V, 2.25–2.75 V, or 3.0–3.6 V) for output buffers. Power sequencing mandates that all VDDO supplies power up before or simultaneously with VDD. Typical total supply current is 27 mA with all 8 outputs active at 3.3 V - SI5351A-B04691-GTR supports efficient mixed-voltage system integration.

Is SI5351A-B04691-GTR pin-compatible with other Si5351 variants?

SI5351A-B04691-GTR uses the 20-pin QFN (4×4 mm) package and shares identical pinout with Si5351A-B-GM and Si5351B-B-GM in the same package. However, pin functionality differs: CLKIN and VC are no-connect on SI5351A-B04691-GTR but active on Si5351B variants. PCB layout is mechanically compatible, but firmware and external circuitry must match the specific variant's capabilities. SI5351A-B04691-GTR is not a drop-in replacement for Si5351B without design review.