Skyworks Solutions Inc. SI5351A-B05949-GM

Overview

SI5351A-B05949-GM from Skyworks Solutions is an I²C-programmable, 8-output CMOS clock generator with integrated crystal oscillator (no external VCXO), supporting frequencies from 2.5 kHz to 200 MHz per output with 0 ppm synthesis error. It operates from a 25 or 27 MHz fundamental-mode AT-cut crystal and delivers low period jitter (<70 ps pk-pk) for timing-critical applications such as audio/video equipment and networking infrastructure.

For engineers reviewing the SI5351A-B05949-GM datasheet, SI5351A-B05949-GM pinout, SI5351A-B05949-GM application, or SI5351A-B05949-GM equivalent, this device enables flexible multi-domain clock synthesis without custom crystals, supports independent output drive strength and rise/fall time control, and offers glitchless frequency changes via I²C configuration.

Technical Context

The SI5351A-B05949-GM implements a dual-PLL architecture with one PLL driven by the internal crystal oscillator (25/27 MHz) and no VCXO path - distinguishing it from Si5351B/C variants. Its eight MultiSynth fractional dividers operate independently, enabling non-integer-related output frequencies up to 200 MHz, with two unique frequencies >112.5 MHz allowed simultaneously.

It uses separate VDD (2.5/3.3 V) and VDDO (1.8/2.5/3.3 V) supplies for core logic and output buffers, provides static phase offset control per output, and supports spread spectrum on each CLKx with selectable center/down-spread modulation at 31.5 kHz.

Key Specifications

Pinout & Package

SI5351A-B05949-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 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 SI5351A-B-GM, SI5351A-B05949-GM saves engineering time by eliminating I²C initialization firmware development, while Si5341-A06469-GM trades cost and simplicity for significantly lower jitter and higher frequency capability - making it appropriate only for next-generation high-speed interfaces.

Availability

SI5351A-B05949-GM is available at Aetrix Electronics and suitable for audio/video equipment, networking infrastructure, and industrial instrumentation requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for SI5351A-B05949-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 timing, RF, and power management ICs.

The Si5351 family was designed specifically for cost-sensitive, multi-clock-domain applications requiring programmable, crystal-replacement clock generation - targeting consumer, industrial, and communications end equipment.

FAQ

What is the exact crystal frequency supported by SI5351A-B05949-GM?

The SI5351A-B05949-GM supports only 25 MHz or 27 MHz fundamental-mode AT-cut crystals as its timing reference. These frequencies feed the internal oscillator that drives both PLLs. No other crystal frequencies (e.g., 10 MHz, 20 MHz) are compatible, and the device does not accept external clock inputs (CLKIN) or VCXO control voltage (VC) - confirming its Si5351A variant identity.

Does SI5351A-B05949-GM require external configuration after power-up?

No. SI5351A-B05949-GM contains a factory-programmed configuration (custom code B05949) stored in on-chip EEPROM. Upon power-up, it automatically loads this configuration and begins generating its pre-defined set of eight output frequencies without host I²C intervention. The I²C interface remains accessible for runtime reconfiguration if needed.

Can SI5351A-B05949-GM generate two 150 MHz outputs simultaneously?

No. SI5351A-B05949-GM adheres to the Si5351 architecture limit: only two *unique* frequencies above 112.5 MHz may be generated at once. So while it can output 150 MHz on CLK0 and CLK1, adding a third distinct frequency >112.5 MHz (e.g., 125 MHz on CLK2) violates the specification. Duplicate frequencies (e.g., 150 MHz on CLK0–CLK3) are permitted.

What is the maximum allowable load capacitance for SI5351A-B05949-GM outputs?

The SI5351A-B05949-GM outputs are specified for a maximum capacitive load of 15 pF per clock pin, as confirmed in Table 7 of the datasheet. Exceeding this value degrades edge rate, increases jitter, and may cause duty cycle distortion - especially critical for high-frequency outputs (>100 MHz). Proper termination and PCB routing must maintain net capacitance ≤15 pF.

How does SI5351A-B05949-GM handle power supply sequencing?

SI5351A-B05949-GM requires that all VDDOx supply rails be powered up either before or simultaneously with the core VDD rail. Delaying VDDOx relative to VDD may cause undefined output states or increased startup time. This sequencing requirement is explicitly defined in Table 3 (Recommended Operating Conditions) and applies across all operating voltages (2.5 V or 3.3 V).