原标题：Silicon Lab Si5338 I2C可编四时钟发生器解决方案

　　Silicon Lab公司的Si5338是I2C可编任意频率任意输出的四个高性能低抖动时钟发生器,时钟频率高达350MHz,可选择频率高达710MHz,器件采用外接晶振支持自由运行操作,或锁住外接时钟产生同步时钟;输出驱动器支持四个差分时钟或八个单端时钟或两者的组合;输出驱动器可配置支持共同信号格式如LVPECL,LVDS,HCSL, CMOS, HSTL 和SSTL.单独输出电源引脚的电源可为3.3V,2.5V,1.8V和1.5V,支持多格式输出驱动器.核电压采用3.3V,2.5V或1.8V,并和输出电源分离.器件的相位抖动为0.7ps RMS,外接晶振为8-30MHz,CMOS输入频率为5-200 MHz,SSTL/HSTL输入频率为5-350 MHz,差分输入频率为5-710MHz,可配置输出频率LVPECL/LVDS为0.16-710 MHz,HCSL为0.16-250 MHz,CMOS为0.16-200 MHz,SSTL/HSTL为0.16-350 MHz.工作温度为–40到+85℃,主要用在以太网交换/路由器,PCIe Gen1/2/3/4,宽带视频/音频定时器,处理器和FPGA时钟,任意频率时钟转换,MSAN/DSLAM/PON,光纤通路,SAN,通信线路卡以及1 GbE和10 GbE.本文介绍了Si5338主要特性,功能框图,应用电路图以及Si5330/34/35/38评估板Si5338-EVB主要特性,框图,电路图,材料清单和PCB设计图.

　　The Si5338 is a high-performance, low-jitter clockgenerator capable of synthesizing four independentuser-programmable clock frequencies up to 350 MHzand select frequencies up to 710 MHz. The devicesupports free-run operation using an external crystal, orit can lock to an external clock for generatingsynchronous clocks. The output drivers support fourdifferential clocks or eight single-ended clocks or acombination of both. The output drivers are configurableto support common signal formats, such as LVPECL,LVDS, HCSL, CMOS, HSTL, and SSTL. Separateoutput supply pins allow supply voltages of 3.3, 2.5, 1.8,and 1.5 V to support the multi-format output driver. Thecore voltage supply accepts 3.3, 2.5, or 1.8 V and isindependent from the output supplies.

　　Using its two-stage synthesis architecture and patentedhigh-resolution MultiSynth technology, the Si5338 cangenerate four independent frequencies from a singleinput frequency. In addition to clock generation, theinputs can bypass the synthesis stage enabling theSi5338 to be used as a high-performance clock buffer ora combination of a buffer and generator.

　　For applications that need fine frequency adjustments,such as clock margining, each of the synthesizedfrequencies can be incremented or decremented inuser-defined steps as low as 1 ppm per step.

　　Output-to-output phase delays are also adjustable inuser-defined steps with an error of <20 ps tocompensate for PCB trace delays or for fine tuning ofsetup and hold margins.A zero-delay mode is also available to help minimizeinput-to-output delay. Spread spectrum is available oneach of the clock outputs for EMI-sensitive applications,such as PCI Express.

　　Configuration and control of the Si5338 is mainlyhandled through the I2C/SMBus interface. Somefeatures, such as output enable and frequency or phaseadjustments, can optionally be pin controlled. Thedevice has a maskable interrupt pin that can be　monitored for loss of lock or loss of input signalconditions.

　　The device also provides the option of storing a userdefinableclock configuration in its non-volatile memory(NVM), which becomes the default clock configurationat power-up.

　　Si5338主要特性:

　　Low power MultiSynth™ technologyenables independent, any-frequencysynthesis on four differential outputdrivers

　　 PCIe Gen 1/2/3/4 Common Clock andGen 3 SRNS compliant

　　 Highly-configurable output drivers withup to four differential outputs, eight

　　single-ended clock outputs, or acombination of both

　　 Low phase jitter of 0.7 ps RMS typ

　　 High precision synthesis allows truezero ppm frequency accuracy on alloutputs

　　 Flexible input reference:

　　External crystal: 8 to 30 MHz

　　CMOS input: 5 to 200 MHz

　　SSTL/HSTL input: 5 to 350 MHz

　　Differential input: 5 to 710 MHz

　　 Independently configurable outputssupport any frequency or format:

　　LVPECL/LVDS: 0.16 to 710 MHz

　　HCSL: 0.16 to 250 MHz

　　CMOS: 0.16 to 200 MHz

　　SSTL/HSTL: 0.16 to 350 MHz

　　 Independent output voltage per driver:1.5, 1.8, 2.5, or 3.3 V

　　 Single supply core with excellentPSRR: 1.8, 2.5, 3.3 V

　　 Independent frequency increment/decrement feature enablesglitchless frequency adjustments in1 ppm steps

　　 Independent phase adjustment oneach of the output drivers with anaccuracy of <20 ps steps

　　 Highly configurable spreadspectrum (SSC) on any output:

　　Any frequency from 5 to 350 MHz

　　Any spread from 0.5 to 5.0%

　　Any modulation rate from 33 to63 kHz

　　 External feedback mode allowszero-delay mode

　　 Loss of lock and loss of signalalarms

　　 I2C/SMBus compatible interface

　　 Easy to use programming software

　　 Small size: 4 x 4 mm, 24-QFN

　　 Low power: 45 mA core supply typ

　　 Wide temperature range: –40 to+85℃

　　Si5338应用:

　　 Ethernet switch/router

　　 PCIe Gen1/2/3/4

　　 Broadcast video/audio timing

　　 Processor and FPGA clocking

　　 Any-frequency clock conversion

　　 MSAN/DSLAM/PON

　　 Fibre Channel, SAN

　　 Telecom line cards

　　 1 GbE and 10 GbE

　　图1.Si5338功能框图

　　图2.Si5338典型应用电路图

　　Si5330/34/35/38评估板Si5338-EVB

　　The Si5338-EVB is used for evaluating the Si5330/34/35/38 family of any-frequency, any-output clockgenerators and clock buffers.

　　评估板Si5338-EVB主要特性:

　　 Fully powered from a single USB port.

　　 Onboard 25 MHz XTAL allows standaloneasynchronous operation on the Si5334/35/38.

　　 GUI programmable VDD supply allows device tooperate from 3.3, 2.5, or 1.8 V.

　　 GUI programmable VDDO supplies allow each of thefour outputs to have its own supply voltageselectable from 3.3, 2.5, 1.8, or 1.5 V

　　 GUI-controlled voltage, current, and powermeasurements of VDD and all four VDDO supplies.

　　 Voltage supply jumpers allow easy access for use ofexternal supplies or current measurements.

　　 Input signal jumpers allow external control of pinfunctions such as output enable, phase inc/dec,frequency inc/dec, and I2C_LSB.

　　图3.评估板Si5338-EVB外形图

　　图4.评估板Si5338-EVB功能框图

　　图5.评估板Si5338-EVB主电路图

　　图6.评估板Si5338-EVB MCU电路图

　　图7.评估板Si5338-EVB电压稳压器电路图

　　评估板Si5338-EVB材料清单: