SI5335B-B03900-GMR
SI5335B-B03900-GMR - 4-Output Any-Frequency Clock Generator | Skyworks
The Skyworks Solutions (formerly Silicon Labs) SI5335B-B03900-GMR is a web-customizable, any-frequency, any-output quad clock generator capable of synthesizing four completely non-integer-related frequencies up to 200 MHz per output (350 MHz on newer revisions per datasheet), all from a single external crystal or reference input. The device uses Skyworks' patented MultiSynth fractional divider technology to guarantee 0 ppm frequency synthesis accuracy on every output. Housed in a 24-pin QFN-EP (4x4 mm) package with an exposed thermal pad, it supports four output banks where each bank delivers one differential pair or two single-ended clocks, giving designers four differential or eight single-ended timing references from a single IC. The 1.8 V core supply and configurable output voltages (1.8 V, 2.5 V, 3.3 V) simplify interfacing with downstream SerDes, FPGA, ASIC, and processor clocks.
A clock generator is a timing IC that produces one or more precision reference frequencies from a single input reference, replacing multiple crystal oscillators and reducing BOM cost. The SI5335 family falls within the broader hierarchy of clock generators -> frequency synthesizers -> PLL-based timing ICs -> clock & timing semiconductors. Unlike fixed-frequency XOs, the SI5335B can be factory- or web-configured to deliver any combination of output frequencies, output formats (LVDS, LVPECL, HCSL, CMOS), and drive strengths, making it a universal replacement for up to four separate oscillators.
Key features include sub-200 ps peak-to-peak output-to-output skew, integrated 50 ohm output termination options, per-bank output enable/disable control, and I2C/SPI host interface for in-system reconfiguration. The internal MultiSynth architecture eliminates the need for external loop filter components and supports glitchless output frequency changes. The 1.8 V core with separate VDDO banks for each output allows mixed-voltage designs where one bank drives 1.8 V LVDS logic while another drives 3.3 V LVPECL PHYs without level translators.
Technical depth: the MultiSynth fractional-N architecture permits arbitrary frequency synthesis with no integer-multiple relationship constraint between outputs. Each MultiSynth block contains its own fractional divider and VCO, so changing one output frequency does not perturb the others. This independence is critical in systems where the application processor, memory controller, PHY, and fabric clocks must run at unrelated rates, eliminating the need for multiple oscillators and reducing board area by up to 80 percent versus discrete XO banks.
Typical applications include FPGA/ASIC reference clock generation, networking switches and routers, server and storage backplanes, broadcast video timing, industrial test and measurement, and any multi-rail system that previously required four separate crystal oscillators. The wide output format support makes it equally suitable for legacy CMOS logic and modern LVDS SerDes interfaces. As a Skyworks ClockBuilder Pro configurable device, every orderable part number such as the B03900-GMR suffix encodes a specific factory-programmed frequency plan, but the silicon itself is identical across the family.
Design consideration: the exposed pad (EP) on the QFN-24-EP package must be soldered to a sufficient ground copper pour for thermal dissipation and low-inductance ground return. Place the input reference crystal within 5 mm of the XIN/XOUT pins and follow the datasheet's four-layer reference layout for skew-critical applications.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet alone.
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