SI53307-B-GM
SI53307-B-GM - 2:2 Low-Jitter Clock Buffer | Skyworks | 725MHz
The Skyworks (formerly Silicon Labs) SI53307-B-GM is a universal 2:2 low-jitter fanout clock buffer and level translator with a pin-selectable output clock signal format, divider selection, and integrated 2:1 input multiplexer, operating from 1 MHz to 725 MHz in a 16-pin QFN exposed-pad package. It features 50 fs typical additive jitter, a glitchless switching mux for redundant clocking, and built-in LDOs that deliver high PSRR while reducing the need for external supply-filtering components. Supply voltage spans 2.97 V to 3.63 V from a single rail.
A clock buffer (also called a fanout buffer) is a type of timing IC that replicates a single reference clock to multiple downstream loads while preserving edge fidelity, frequency, and phase. Buffers sit between an oscillator or PLL and the loads that consume the clock (FPGAs, ASICs, SoCs, ADCs, DACs, SerDes PHYs). Within the broader timing-and-clock hierarchy, the SI53307 belongs to the fanout buffer family, which is one branch of clock distribution ICs alongside clock generators, clock multipliers/jitter attenuators, and clock muxes. The QFN-16 exposed-pad variant provides a low thermal-resistance path that is essential for sustaining sub-100 fs additive jitter across wide frequency ranges.
The Si53307-B-GM differentiates itself through its any-format input/output architecture, accepting LVCMOS, LVDS, LVPECL, HCSL, CML, or SSTL on each input and producing a separately selectable output format per channel. Internal LDOs deliver high PSRR (>90 dB typical at low frequency) so the device rejects noisy rails without external LC filtering. Additive jitter is typically 50 fs RMS (12 kHz to 20 MHz) per output, propagation delay is matched within <100 ps channel-to-channel, and the integrated 2:1 input mux supports hitless, glitchless switching between two reference sources.
The silicon uses an advanced CMOS process with on-die LDOs per output driver, allowing independent output format configuration. Output skew is held under 50 ps, and the divider block supports ÷1, ÷2, ÷4, ÷8, ÷16, ÷32, ÷64 per output, all pin-selectable. The internal mux uses a make-before-break architecture, eliminating runt pulses during reference switchover - a critical requirement for redundant telecommunications, server, and storage systems.
Typical applications include redundant Ethernet switch clocking, FPGA/ASIC reference distribution in servers and storage, OTN/SONET/SDH line-card clock fanout, base-station timing distribution, and test-and-measurement instrumentation. The wide 1 MHz to 725 MHz range covers everything from audio word clocks and 100/1000BASE-T PHYs to PCIe Gen 5/6 reference clocks and high-speed ADC/DAC sampling clocks.
Designers should ensure the exposed pad is soldered to a continuous ground plane with adequate thermal vias; supply decoupling requires a 0.1 µF X7R capacitor placed within 2 mm of the VDD pin. Output format selection must be set before VDD ramps above 0.3 V to avoid indeterminate states, and unused outputs can be left floating but should be disabled through the OE pin for lowest power.
This page synthesizes distributor pricing, drop-in same-family alternatives, and practical design notes not found in the manufacturer datasheet alone.
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