SI5351B-B04778-GM

Clock Generators, PLLs, Frequency Synthesizers Overview

The Skyworks SI5351B-B04778-GM is an I2C-programmable CMOS clock generator housed in a 20-QFN package. It features two PLLs and eight MultiSynth fractional dividers to generate up to eight independent output frequencies ranging from 2.5 kHz to 200 MHz with 0 ppm error. The device integrates a Voltage-Controlled Crystal Oscillator (VCXO) for synchronous clock generation, eliminating the need for custom pullable crystals. It operates on core supply voltages of 2.5 V or 3.3 V and supports output voltage levels of 1.8 V, 2.5 V, or 3.3 V.

Clock Generators, PLLs, Frequency Synthesizers Feature Summary

• Integrates a highly linear VCXO architecture to replace higher cost custom pullable crystals while providing reliable operation over a wide tuning range.
• Generates multiple non-integer-related frequencies using high-resolution MultiSynth fractional dividers driven by dual PLLs.
• Supports configurable spread spectrum modulation at each output to minimize electromagnetic interference.
• Features separate voltage supply pins for level translation between core logic and output buffers.

Clock Generators, PLLs, Frequency Synthesizers Applications

• Replacing crystals, crystal oscillators, VCXOs, and phase-locked loops in cost-sensitive designs.
• Generating system clocks for audio/video equipment and gaming consoles.
• Providing timing signals for networking, communication, servers, and storage systems.
• Serving as a replacement for XO components in handheld instrumentation.

Clock Generators, PLLs, Frequency Synthesizers Procurement Notes

Verify that the specific ordering suffix matches the required factory preprogrammed configuration. Confirm the package type corresponds to the 20-QFN variant. Ensure the component source is authorized to guarantee authenticity and compliance with RoHS standards.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select this model when both free-running asynchronous clocks and synchronous VCXO-controlled outputs are required within a single device. Compare against Si5351A if VCXO functionality is unnecessary, or Si5351C if synchronization to an external reference clock is preferred over internal VCXO control.

Clock Generators, PLLs, Frequency Synthesizers Part Context

This component belongs to the Si5351A/B/C-B family of I2C programmable clock generators. The 'B' designation specifically indicates the inclusion of an internal VCXO, distinguishing it from the Si5351A which lacks this feature and the Si5351C which synchronizes to an external CLKIN input.

Clock Generators, PLLs, Frequency Synthesizers Replacement Considerations

Si5351B-B-GM serves as a blank alternative requiring user programming. Si5351A-B-GM is suitable if VCXO capabilities are not needed. Si5351C-B-GM should be considered if external reference clock synchronization is required instead of internal VCXO tuning.

Clock Generators, PLLs, Frequency Synthesizers FAQ

How does the Si5351B handle frequency synthesis above 112.5 MHz?

Only two unique frequencies above 112.5 MHz can be simultaneously output. Multiple copies of a single high-frequency output can be provided on different pins, but distinct high frequencies must be limited to two concurrent channels.

What is the purpose of the VC pin on the Si5351B?

The VC pin accepts a control voltage to tune the internal VCXO. This allows the device to generate multiple output frequencies that are all controlled by the same reference voltage, replacing the need for multiple external PLLs or VCXOs.

Can the Si5351B operate without an external crystal?

No, the Si5351B requires a standard fixed-frequency AT-cut crystal (typically 25 or 27 MHz) connected to the XA and XB pins to serve as the reference for the internal oscillator and VCXO.