Skyworks Solutions Inc. SI5351B-B04481-GM

Overview

SI5351B-B04481-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 embedded 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, and operates from a 25 or 27 MHz fixed-frequency crystal.

For engineers reviewing the SI5351B-B04481-GM datasheet, SI5351B-B04481-GM pinout, SI5351B-B04481-GM application, or SI5351B-B04481-GM equivalent, this device is selected for designs requiring flexible multi-domain clocking with VCXO tuning capability, low jitter (<70 ps pk-pk), and independent output voltage scaling (1.8/2.5/3.3 V).

Technical Context

The SI5351B-B04481-GM implements a dual-PLL architecture: PLL A accepts either XTAL or CLKIN input, while PLL B functions as a highly linear VCXO locked to the same crystal reference. Both PLLs feed eight independent MultiSynth fractional dividers, enabling precise, glitchless frequency synthesis per output.

It features configurable spread spectrum on each output, static phase offset control, programmable rise/fall times, and separate VDD (2.5/3.3 V) and VDDO (1.8/2.5/3.3 V) supplies for level translation. The VC pin accepts 0–VDD control voltage, delivering ±240 ppm pull range with ±5% linearity at 3.3 V supply.

Key Specifications

Pinout & Package

SI5351B-B04481-GM is housed in a 20-pin QFN package (4 mm × 4 mm, 0.5 mm pitch) with exposed thermal pad. Pin assignments 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 SI5351B-B04481-GM, the Si5351A-B-GM omits VCXO tuning entirely, limiting use to open-loop timing; the Si5351C-B-GM replaces VC with CLKIN, enabling synchronization but removing analog control - making SI5351B-B04481-GM uniquely suited for applications requiring both crystal-based stability and voltage-adjustable frequency pulling.

Availability

SI5351B-B04481-GM is available at Aetrix Electronics and suitable for networking equipment, audio/video systems, laser range finders, and industrial instrumentation requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for SI5351B-B04481-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, timing, and broadband infrastructure markets.

The Si5351 family was engineered to consolidate timing functions in space-constrained, cost-sensitive embedded systems - delivering programmable multi-output clock generation with VCXO flexibility previously found only in higher-cost discrete solutions.

FAQ

What is the maximum number of unique frequencies above 112.5 MHz that SI5351B-B04481-GM can generate simultaneously?

The SI5351B-B04481-GM supports only two unique frequencies above 112.5 MHz at any time - for example, 125 MHz and 130 MHz. Additional outputs may replicate those frequencies, but no third distinct frequency >112.5 MHz is permitted. This limitation arises from internal PLL bandwidth and MultiSynth divider resolution constraints documented in Table 7 of the Skyworks datasheet Rev. 1.3.

Does SI5351B-B04481-GM require external load capacitors for its 25 MHz crystal?

SI5351B-B04481-GM includes programmable internal load capacitance (0, 6, 8, or 10 pF) and typically requires no external capacitors for standard 6–10 pF-load crystals. For 12 pF crystals, ≤2 pF total external capacitance (e.g., 4 pF split across XA/XB) is recommended per AN551. The device's internal oscillator circuit is optimized for 25 or 27 MHz AT-cut crystals without additional passive components.

Can SI5351B-B04481-GM generate HCSL-compatible output levels?

Yes - SI5351B-B04481-GM supports HCSL-compatible swing through programmable output drive strength and termination control. When configured with 50 Ω output impedance and appropriate VDDO (typically 2.5 V), it delivers differential-like swing suitable for HCSL-receiver inputs. This capability is explicitly confirmed in the "Features" section and Application Note AN551.

What is the guaranteed VCXO linearity specification for SI5351B-B04481-GM at 3.3 V supply?

At 3.3 V supply, SI5351B-B04481-GM guarantees ±5% VCXO control voltage linearity over the 10–90% VDD range (0.33–2.97 V), as specified in Table 5 of the Skyworks datasheet Rev. 1.3. This ensures predictable, monotonic frequency pulling behavior essential for closed-loop calibration and servo applications.

Is SI5351B-B04481-GM pin-compatible with other Si5351 variants in the 20-QFN package?

Yes - SI5351B-B04481-GM shares identical 20-QFN pinout and footprint with Si5351A-B-GM and Si5351C-B-GM, as confirmed in Section 10.2 of the Skyworks datasheet. All three variants use the same mechanical outline, thermal pad layout, and signal pin assignments, enabling drop-in replacement where functional compatibility exists.