Skyworks Solutions Inc. SI5351A-B06856-GM

Overview

SI5351A-B06856-GM from Skyworks Solutions is an I²C-programmable, 8-output CMOS clock generator with integrated VCXO architecture, generating free-running and synchronous clocks from 2.5 kHz to 200 MHz with 0 ppm frequency error. It operates from a 25 or 27 MHz crystal, supports independent 1.8/2.5/3.3 V output supplies, and delivers <70 ps pk-pk period jitter in 20-QFN package for embedded timing replacement applications.

For engineers reviewing the SI5351A-B06856-GM datasheet, SI5351A-B06856-GM pinout, SI5351A-B06856-GM application, or SI5351A-B06856-GM equivalent, key selection criteria include its 8-output capability, VCXO tuning range (±240 ppm at 3.3 V), I²C configurability, HCSL-compatible swing support, and PCIe Gen 1 compliance-critical for multi-domain clock synthesis in space-constrained designs.

Technical Context

The SI5351A-B06856-GM implements a dual-PLL architecture (PLLA + PLLB) with high-resolution MultiSynth fractional dividers per output, enabling independent non-integer-related frequency synthesis. Its VCXO path uses a single control voltage (VC pin) to tune both PLLs simultaneously, eliminating external pullable crystals while maintaining ±5% linearity across 10–90% of VDD.

Each of the eight outputs features programmable rise/fall time, static phase offset, spread spectrum (±0.1–±2.5% deviation), and glitchless frequency transitions. The device accepts only XTAL input (no CLKIN), confirming it as Si5351A variant-distinct from Si5351B/C which support VC or external reference inputs.

Key Specifications

Pinout & Package

SI5351A-B06856-GM is housed in a 20-pin QFN (4 mm × 4 mm, 0.5 mm pitch) package with exposed thermal pad. Pin functions are validated per Skyworks Si5351A 20-pin QFN specification (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 Si5351B-B-GM and Si5351C-B-GM, SI5351A-B06856-GM provides lowest-cost crystal-referenced 8-output clock generation without VC or CLKIN dependencies-ideal for fixed-frequency, cost-sensitive applications where external tuning or synchronization is unnecessary.

Availability

SI5351A-B06856-GM is available at Aetrix Electronics and suitable for networking equipment, audio/video timing systems, laser range finders, and handheld instrumentation requiring stable component supply, long-term lifecycle support, and consistent electrical performance across temperature.

Supply support for SI5351A-B06856-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 semiconductor company specializing in analog and mixed-signal connectivity solutions, with leadership in RF, timing, and power management technologies.

The Si5351 family is designed for flexible, low-cost clock generation in space-constrained embedded systems-replacing crystals, oscillators, and discrete PLLs with a single I²C-configurable IC supporting multi-domain timing requirements.

FAQ

What is the maximum number of unique frequencies above 112.5 MHz that SI5351A-B06856-GM can generate simultaneously?

SI5351A-B06856-GM supports only two unique frequencies above 112.5 MHz at once-for example, 125 MHz on CLK0 and 130 MHz on CLK1. Additional outputs above 112.5 MHz must duplicate one of those two frequencies. This limitation arises from internal PLL bandwidth constraints and is specified in Table 7 of the Skyworks datasheet Rev. 1.3. SI5351A-B06856-GM enforces this rule in hardware to maintain jitter performance and frequency stability.

Does SI5351A-B06856-GM support external clock input (CLKIN) or only crystal reference?

SI5351A-B06856-GM supports crystal reference only (XA/XB pins) and does not support external CLKIN. It is the Si5351A variant, distinct from Si5351B (VCXO + XTAL) and Si5351C (CLKIN + XTAL). The absence of CLKIN functionality is confirmed in the functional block diagram (page 2) and ordering guide (Table 1), where SI5351A-B-GM part numbers are explicitly listed as "XTAL only." SI5351A-B06856-GM requires a 25 or 27 MHz crystal for operation.

What is the VCXO capability of SI5351A-B06856-GM, and how does it differ from Si5351B?

SI5351A-B06856-GM does not include VCXO functionality-it lacks the VC pin and associated tuning circuitry. Only Si5351B variants (e.g., Si5351B-B-GM) provide VCXO support with ±240 ppm pull range at 3.3 V. SI5351A-B06856-GM generates free-running clocks only. This distinction is clearly defined in the product description (page 1): "The Si5351A generates up to 8 free-running clocks using an internal oscillator," whereas Si5351B "adds an internal VCXO."

Can SI5351A-B06856-GM generate HCSL-compatible output swings?

Yes, SI5351A-B06856-GM supports HCSL-compatible output swing through programmable drive strength and termination control. As stated in the Features section (page 1), it "Supports HCSL compatible swing." This is achieved by configuring output impedance (50 Ω default) and voltage levels (VOH ≥ VDD – 0.6 V, VOL ≤ 0.6 V) to meet HCSL differential pair requirements when used with appropriate external termination. SI5351A-B06856-GM achieves this without additional level-shifting components.

What package type and thermal characteristics apply to SI5351A-B06856-GM?

SI5351A-B06856-GM uses the 20-pin QFN package (4 mm × 4 mm, 0.5 mm pitch) with exposed thermal pad. Per Table 12 (Rev. 1.3), its thermal resistance is θJA = 41 °C/W on a 4-layer board and ΨJB = 16 °C/W (junction-to-board), enabling reliable operation up to +85 °C ambient with minimal heatsinking. This package matches the pinout and land pattern defined in Section 12.2 of the datasheet.