SiTime, Silicon MEMS Oscillators and Clock Generators

SiTime’s Programmable Silicon MEMS Oscillator Improves Ethernet System BER (Bit Error Rate)

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Packet losses in Ethernet-based networking systems are critical errors that can lead to significant degradation in network performance. In the past, packet loss problems were usually overcome by redesigning the board. Over time, another popular technique for reducing packet losses emerged: Increase the reference clock frequency to Ethernet chipsets.

Ethernet chipsets typically use standard reference frequencies such as:

  • 156.25MHz for 10 Gigabit Ethernet
  • 125MHz for Gigabit Ethernet, GPON and EPON
  • 25MHz for 100 Base-T Ethernet.


In certain network configurations or board designs, packet losses can be eliminated by increasing the reference clock by 25 PPM or 50 PPM, a technique also known as PLUS PPM CLOCKING. This technique involves using custom frequencies such as 156.25391MHz, 125.00375MHz or 25.000625MHz to drive Ethernet chipsets.

Such customized frequencies are available from quartz crystal suppliers with 12 to 16 weeks leadtime, which does not solve the immediate problem. Customers would rather redesign the board than wait for these custom frequencies to be delivered.

SiTime solves this availability problem with its programmable oscillator platform. SiTime can ship customized samples in as little as 48 hours, and make production quantities available in 2 to 4 weeks. The flexibility of SiTime's programmable Silicon MEMS oscillators enables system suppliers to employ such error-reducing techniques that enhance system performance without sacrificing oscillator lead time, cost and reliability.

SiTime's SiT82xx and SiT91xx ultra performance oscillators are based on SiTime's high performance programmable platform which offers the following options.

  • Any frequency between 1 to 220 MHz with 6 decimal places of accuracy
  • Any frequency stability from ±10 PPM to ±50 PPM
  • -20 ºC to 70 ºC or -40 ºC to 85 ºC operating temperature range
  • 1.8V or 2.5 to 3.3 V operations

Instant samples in any frequency, frequency stability, supply voltage and drive strength can be programmed in the customer's lab using SiTime's Time Machine II and field programmable devices.

SiTime's MEMS Oscillator Solutions for Ethernet Systems BER

Applications

SiTime Device

Device Specification

10 Gigabit Ethernet

SiT8209AI-32-33E-156.2500000

156.25MHz, 5032 package, 3.3V, ±25 PPM

10 Gigabit Ethernet

SiT8209AI-32-33E-156.253910

156.25MHz w/ 25PPM freq shift, 5032 package, 3.3V, ±25 PPM

1 Gigabit Ethernet or GPON/EPON

SiT8209AI-32-33E-125.000000

125MHz , 5032 package, 3.3V, ±25 PPM

1 Gigabit Ethernet or GPON/EPON

SiT8209AI-32-33E-125.003750

125MHz w/ 50PPM freq shift, 5032 package, 3.3V, ±25 PPM

100 Base-T or 1 Gigabit Ethernet

SiT8208AI-32-33E-25.000000

25MHz, 5032 package, 3.3V, ±25 PPM

100 Base-T or 1 Gigabit Ethernet

SiT8208AI-32-33E-25.000625

25MHz w/ 50PPM freq shift, 5032 package, 3.3V, ±25 PPM

PCI-E

SiT9120AI-32-33E-133.330000

133.3MHz, 5032 package, 3.3V, ±25 PPM

System Processor

SiT8008AI-83-33E-66.667000

66.667MHz, 7050 package, 3,3V, ±50PPM

 

 

SiTime products also offer the following options for customization

  • Any frequency between 1 and 220 MHz with 6 decimal places of accuracy
  • Operation at 1.8V, 2.5V, 2.8V or 3.3V, configurable.
  • 2520, 3225, 5032 and 7050 packages
  • Configurable Rise/Fall times (Drive Strength) for EMI reduction
  • Configurable Output Load Control

Ethernet-block-diagram

Frequently used device:

SiT8208AI-32-33E-25.000625 MHz 
50 PPM shift from standard 25 MHz reference
±25 PPM stability
3.3V voltage supply voltage

Click here for other possible SiT8208 configurations

Frequently used device:

SiT8209AI-32-33E-133.33 MHz
±25 PPM stability
3.3V voltage supply voltage

Click here for other possible SiT8209 configurations

Frequently used device:

SiT8103AI-83-33E-66.667000 MHz
50 PPM stability
3.3V voltage supply voltage

Click here for other possible SiT8103 configurations

Frequently used device:

SiT8209AI-32-33E-156.253910 MHz 
50 PPM shift from standard 156.25 MHz reference
±25 PPM stability
3.3V voltage supply voltage

Click here for other possible SiT8209 configurations

Frequently used device:

SiT8209AI-32-33E-125.000325 MHz 
25 PPM shift from standard 125 MHz reference
±25 PPM stability
3.3V voltage supply voltage

Click here for other possible SiT8209 configurations

Depending on the design, some blocks may not be necessary.

SiTime products also offer the following options for customization

  • Any frequency between 1 and 220 MHz with 6 decimal places of accuracy
  • Operation at 1.8V, 2.5V, 2.8V or 3.3V, configurable.
  • 2520, 3225, 5032 and 7050 packages
  • Configurable Rise and Fall times (Drive Strength) for EMI reduction
  • Configurable Output Load Control

 

 

Design Considerations MEMS Oscillator Features
  • Eliminate network packet loss
  • Configurable frequency skew at ±25 PPM and ±50 PPM of base frequency
  • Meet carrier requirements such as drop-test
  • 50 KG shock resistance
    70 G vibration resistance
  • Same availability (production volume) of custom frequency devices as standard frequencies
  • Ability to create instant samples in any frequency
  • 2 to 4 weeks leadtime for production volume, best in the industry for any combination of frequency, stability, voltage, package and other factory-programmable features
  • Minimize field failures and costly filed service calls
  • 500 million hour MTBF
  • Enhance system robustness with better timing margin
  • ±10 PPM stability over the entire operating temperature range
    Insensitive to temperature variations