Top of Rack Switch / Leaf Switch

IEEE 1588 is becoming the de facto standard for better performance in data centers. As Synchronous Ethernet (SyncE) replaces Ethernet, use of a TCXO or OCXO reference clock in top-of-rack and leaf switch is needed. SiTime offers a complete MEMS-based clock tree solution that performs better in real-world operating conditions.

Elite Platform® Super-TCXOs® and Emerald OCXOs provide essential stability and reduce time error through better frequency over temperature slope. Cascade™ network synchronizers / jitter cleaners / clock generators, used to filter jitter in recovered clocks, have an integrated resonator that simplifies development and reduces field failures. When SyncE and IEEE 1588 are not needed, SiTime differential oscillators offer sub-100-femtosecond jitter and low power. Together they offer a complete and robust clock tree.

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SiTime MEMS Timing Benefits

Complete MEMS clock tree

Integrated MEMS

Stratum 3E MEMS OCXO

MEMS clock IC/PLL

More robust in real world conditions

4x better dF/dT for best time sync

70 fs rms jitter, excellent PSNR

Resistant to airflow, heat, vibration

Integrated MEMS, easy to use

No external quartz

No quartz reliability issues

No cover or shielding needed

Top of Rack Switch / Leaf Switch Block Diagrams

MEMS Timing Solutions with SyncE and IEEE 1588

MEMS Timing Solutions without SyncE and IEEE 1588

MEMS XO + Buffer Alternative Timing Solution

MEMS Timing Solutions

Devices	Function	Key Features
Super-TCXO SiT535x 1 to 220 MHz	Reference clock for jitter cleaner and IEEE1588	±100 ppb, ±1 ppb/°C 105°C
OCXO SiT57xx 1 to 60 MHz	Reference clock for jitter cleaner and IEEE1588	±5 ppb, ±0.04 ppb/°C
Clock Generator SiT9514x 8 kHz to 2.1 GHz	Ethernet	4-in, 11-out, 4-PLL
Network Synchronizer SiT9514x 8 kHz to 2.1 GHz	Ethernet, processor	4-in, 11-out, 4-PLL
Differential XO SiT9501 25 to 644.53125 MHz SiT9375 25 to 644.53125 MHz	Ethernet, FPGA	0.07 to 0.25 ps jitter, 105°

What is a Top of Rack (ToR) Switch?

A leaf switch (or top-of-rack ToR switch) aggregates server traffic between the spine switches and either the core network or servers in the data-center campus. As bandwidth increases in next-gen deployments, higher performance is specified by IEEE 1588, placing a greater demand for high-performance timing solutions that withstand airflow, heat, and vibration.

MEMS Timing Outperforms Quartz

Better Stability	Better Frequency Slope
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Better Vibration Resistance	Better Allan Deviation
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Excellent Phase Noise, 156.25 MHz	Better PSNR (Power Supply Noise Rejection)
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Watch Video: SiTime Elite Super-TCXO Dynamic Performance vs. Quartz TCXO

Application Notes and Papers

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Top of Rack Switch / Leaf Switch