Skyworks Solutions Inc. SI5351B-B04745-GM

Overview

SI5351B-B04745-GM from Skyworks Solutions is an I²C-programmable, 8-output CMOS clock generator with integrated VCXO, designed to replace crystals, crystal oscillators, and voltage-controlled oscillators in cost-sensitive timing applications. It delivers up to eight non-integer-related frequencies from 2.5 kHz to 200 MHz per output, supports 0 ppm frequency synthesis error, operates from a 25 or 27 MHz fixed-frequency crystal, and features low period jitter (< 70 ps pk-pk) for precision timing in networking and audio/video systems.

For engineers reviewing the SI5351B-B04745-GM datasheet, SI5351B-B04745-GM pinout, SI5351B-B04745-GM application, or SI5351B-B04745-GM equivalent, key selection considerations include its dual-PLL + MultiSynth fractional divider architecture, VCXO tuning range (±240 ppm at 3.3 V), independent VDDO supply pins (1.8/2.5/3.3 V), and support for HCSL-compatible swing and spread-spectrum modulation per output.

Technical Context

The SI5351B-B04745-GM implements a two-stage synthesis architecture: PLL A (SSC-capable) and PLL B (VCXO-based), both fed by either an internal 25/27 MHz crystal oscillator or external CLKIN (10–100 MHz). Each PLL drives eight independent MultiSynth fractional dividers, enabling simultaneous generation of non-integer-related frequencies across all outputs.

It supports static phase offset control, glitchless frequency transitions, programmable rise/fall times, and configurable spread spectrum (down-spread: –0.1% to –2.5%; center-spread: ±0.1% to ±1.5%) at each output. The VCXO exhibits highly linear gain (18–150 ppm/V) and ±5% linearity over 10–90% VDD control voltage range.

Key Specifications

Pinout & Package

SI5351B-B04745-GM is housed in a 20-pin QFN package (4 mm × 4 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are validated per Skyworks Si5351B 20-QFN pinout specification (Rev. 1.3, Section 10.2).

Key Features

Applications

Equivalent & Alternatives

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

Compared with Si5351A-B-GM and Si5351C-B-GM, the SI5351B-B04745-GM uniquely integrates a highly linear VCXO enabling wide-range, voltage-controlled frequency adjustment without external components-making it optimal for applications requiring dynamic tuning stability over temperature and voltage, such as laser ranging and instrumentation.

Availability

SI5351B-B04745-GM is available at Aetrix Electronics and suitable for networking equipment, audio/video systems, laser range finders, and handheld instrumentation requiring stable component supply, long-term lifecycle support, and consistent electrical performance across temperature and voltage ranges.

Supply support for SI5351B-B04745-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 leader in semiconductor innovation, specializing in analog and mixed-signal technologies for wireless, broadband, automotive, and industrial markets.

The Si5351 family is engineered for high-precision, low-cost clock generation in resource-constrained systems-delivering programmable multi-frequency synthesis, VCXO capability, and flexible voltage operation to replace discrete timing components.

FAQ

What is the primary function of the SI5351B-B04745-GM in a timing system?

The SI5351B-B04745-GM serves as an I²C-programmable, 8-output CMOS clock generator with integrated VCXO. Its primary function is to replace multiple discrete crystals, crystal oscillators, and VCXOs by generating up to eight independent, non-integer-related frequencies (2.5 kHz to 200 MHz) with 0 ppm synthesis error. In practice, the SI5351B-B04745-GM enables single-chip clock provisioning for complex multi-domain systems like networking gear and AV equipment.

Does the SI5351B-B04745-GM require an external crystal, and what specifications must it meet?

Yes, the SI5351B-B04745-GM requires a 25 MHz or 27 MHz AT-cut crystal connected to XA/XB pins. Per Skyworks documentation, the crystal must have load capacitance of 6–12 pF, ESR ≤ 150 Ω, and drive level ≤ 100 µW. Internal load capacitance options (0/6/8/10 pF) eliminate need for external caps for standard crystals; optional ≤2 pF external caps may be added for 12 pF crystals.

How does the VCXO feature of the SI5351B-B04745-GM differ from the Si5351A and Si5351C variants?

The SI5351B-B04745-GM includes a dedicated VC pin enabling voltage-controlled frequency tuning (±240 ppm at 3.3 V), whereas Si5351A lacks VCXO entirely and Si5351C replaces VC with CLKIN for external reference synchronization. Only the SI5351B-B04745-GM supports analog voltage-based frequency pulling-making it uniquely suited for applications like laser rangefinders where environmental drift compensation is critical.

Can the SI5351B-B04745-GM generate frequencies above 112.5 MHz, and what limitations apply?

Yes, the SI5351B-B04745-GM supports frequencies up to 200 MHz per output, but only two *unique* frequencies above 112.5 MHz may be active simultaneously (e.g., 125 MHz and 130 MHz). Multiple outputs may replicate the same high-frequency signal (e.g., four 125 MHz clocks), but three distinct frequencies >112.5 MHz (e.g., 125/130/150 MHz) violate the device's synthesis constraint and will not function correctly.

What are the power supply requirements for the SI5351B-B04745-GM, and how do they impact system design?

The SI5351B-B04745-GM requires a core VDD supply (2.25–2.75 V or 3.0–3.6 V) and up to four independent VDDO supplies (1.71–1.89 V, 2.25–2.75 V, or 3.0–3.6 V) for its output banks. Power sequencing mandates that all VDDO rails power up before or concurrently with VDD. This flexibility enables direct interfacing with mixed-voltage logic (e.g., 1.8 V FPGAs and 3.3 V PHYs) without external level shifters-reducing component count and layout complexity.