Skyworks Solutions Inc. SI5351A-B04683-GT

Overview

SI5351A-B04683-GT from Skyworks Solutions is an I²C-programmable, 8-output CMOS clock generator with integrated VCXO and fractional MultiSynth architecture. It synthesizes up to eight independent, non-integer-related frequencies from 2.5 kHz to 200 MHz with 0 ppm frequency error, using a 25 or 27 MHz crystal reference. It serves as a drop-in replacement for crystals, XO, VCXO, and PLL-based clock trees in compact embedded timing systems.

For engineers reviewing the SI5351A-B04683-GT datasheet, SI5351A-B04683-GT pinout, SI5351A-B04683-GT application, or SI5351A-B04683-GT equivalent, this device delivers programmable rise/fall time control, static phase offset, glitchless frequency changes, and independent output voltage supply (1.8/2.5/3.3 V) - critical for multi-rail SoC clocking and jitter-sensitive interfaces like PCIe Gen 1 and HCSL-compatible receivers.

Technical Context

The SI5351A-B04683-GT implements a dual-PLL architecture (PLLA + PLLB) with high-resolution MultiSynth fractional dividers per output. Its input stage accepts only a fixed-frequency crystal (25 or 27 MHz) - no CLKIN or VC pin support - confirming it is the Si5351A variant. All eight outputs are derived from PLLA, with no VCXO tuning capability.

Each output features independent configuration of spread spectrum (±0.1% to ±1.5%), duty cycle (45–55% below 160 MHz), and drive strength. Output jitter is specified at ≤95 ps pk-pk period jitter (all outputs active, 20-QFN package), validated under 2.5 V or 3.3 V core supply and 1.8/2.5/3.3 V output buffer supplies.

Key Specifications

Pinout & Package

SI5351A-B04683-GT 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-B04683-GT, Si5351A-B-GM offers identical hardware but requires full software configuration, while Si5351B-B-GM adds VCXO functionality at the cost of losing crystal-only simplicity - making SI5351A-B04683-GT optimal for fixed-frequency, low-jitter, drop-in crystal replacement.

Availability

SI5351A-B04683-GT is available at Aetrix Electronics and suitable for audio/video equipment, networking/communication infrastructure, and industrial instrumentation requiring stable component supply, long-term lifecycle support, and guaranteed factory-programmed configuration.

Supply support for SI5351A-B04683-GT 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 semiconductors, specializing in RF, mobile, and timing solutions with over 30 years of RF and clocking expertise.

The Si5351 family was designed specifically for cost-sensitive, space-constrained applications needing flexible, high-accuracy clock synthesis - targeting consumer electronics, embedded systems, and industrial control where crystal proliferation increases cost and design risk.

FAQ

What is the factory-programmed configuration of the SI5351A-B04683-GT?

The SI5351A-B04683-GT is preconfigured using ClockBuilder Pro to deliver eight specific output frequencies optimized for common multi-domain timing use cases. Unlike blank variants, it powers up with valid clocks immediately - no I²C initialization required. The exact frequency plan is documented in Skyworks' custom part database and can be retrieved via the 5-digit code "B04683".

Does the SI5351A-B04683-GT support external clock input (CLKIN) or VC tuning?

No. The SI5351A-B04683-GT is the Si5351A variant and supports only a 25 or 27 MHz crystal reference via XA/XB pins. It lacks CLKIN and VC pins entirely - confirmed by its functional block diagram, pinout table (Section 10.1), and ordering guide entry specifying "XTAL only" frequency reference. This makes it incompatible with systems requiring external reference locking or voltage-controlled tuning.

What is the maximum number of unique frequencies above 112.5 MHz supported by the SI5351A-B04683-GT?

The SI5351A-B04683-GT supports exactly two unique frequencies above 112.5 MHz simultaneously - a hard architectural limit of the MultiSynth divider architecture. For example, it may output 125 MHz on CLK0 and 133.333 MHz on CLK1, but adding a third distinct frequency >112.5 MHz (e.g., 150 MHz on CLK2) will cause undefined behavior or failure to lock. This constraint applies regardless of output count or package type.

Can the SI5351A-B04683-GT generate spread spectrum clocking on individual outputs?

Yes. Each of the eight outputs supports independent spread spectrum configuration - down-spread (–0.1% to –2.5%) or center-spread (±0.1% to ±1.5%) - controlled via dedicated register bits. Modulation occurs at 31.5 kHz (typical), and the feature can be enabled or disabled per output without affecting others. This allows targeted EMI reduction on noise-sensitive interfaces (e.g., USB, HDMI) while maintaining tight jitter on critical clocks (e.g., PCIe reference).

What are the thermal limits and PCB layout requirements for reliable operation of the SI5351A-B04683-GT?

The SI5351A-B04683-GT has a maximum junction temperature of 150 °C and requires a 4-layer PCB with thermal vias under the exposed pad for optimal θJA = 41 °C/W. Per Skyworks datasheet Table 11, minimum copper area around the 20-QFN pad should be ≥100 mm² with ≥6 thermal vias (0.3 mm diameter, filled). Core supply decoupling requires one 100 nF ceramic capacitor per VDD pin and one 4.7 µF bulk capacitor within 10 mm of the package.