FEA


FEAT RE ATURE


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NTERCONNE


ONNECTIION O N


Fast track: How next-g eneratio n interconnects enable high-speed data


Contin dev


Plans for 400Gb ps speedswllm an no rest for con ector designers, says JairoG errero, director o f marketing enterprise busin ss unt Molex LLC. Here’


rketing, enterprise business uniit at , re on w o to tackle these challenges T


he need to transmitmore data at higher speeds is changing system


design. New strategies include developing connectors with high-speed features and capabilities,maintaining signal integrity at high speeds and using new protocols. For example, it’s becoming apparent that PAM4 will play a growing role in this transition. Industry standa return-to-zero) signalling


is giving way to rd NRZ (non-


PAM4modulation inmany applications due to PAM4’s ability to process data rates of 100Gbps and higher.


While PAM4 offers speed improvements, datamust be encoded prior to


transmission, then decoded when received. This additional stepmakes PAM4more challenging to implement. Still, where high speeds are critical, PAM4’s additional capabilities balance out it s higher processing costs.


However, NRZ is still appropriate for certain high-speed applications. New provide data h PAM4 and


rates above 50Gbps in bot backplane connectors can


NRZ systems. When speeds increase, traditional


connector challenges aremagnified. For example, higher data speed channels typically involve increased electromagnetic interference, higher crosst alk an d impedance discontinuities. Also,


connectors typically have to work with existing headers (ensuring backw


kwards


compatibility), enabling integration into existing designs.


Another issue ismaintaining appropriate signal integrity. One solution is to remove high-speed signals fromthe PCB by applying high-speed copper cable. This alternative can be used with both 50Gbps NRZ and PAM4 live, encoded serial traffic using QSFP cable assemblies and connector interfaces.


TOOL OOLS THA HAT EXPEDITE DESIGN AT EXPEDITE DESIGN


With new designs required for high-speed connectors, tools that reduce the time required to simulate systemdesign are welcome. Traditionally, each component is


28 28 DECEMBER JANUAR 2018 ECEMBER/JANUARY 2018 || ELEC RO ELECTRONICS CS Figure 2: Figure 2:


zQS P Plus to zQS P Plus Cable


zQSFP Plus to zQSF Plus Cable


Figure 1: NeoPress family


NeoPress family Figure 1:


simulated independently,meaning it can take a week ormore to simulate designs. However, new software-based design tools employ libraries of pre-simulated models based on typical designs,materials and traces. Designers select the desired models and get results almost ,


immediately allowing first-order system approximation and giving themnew insight into critical parameters for


developing new systems. Designers being tasked with getting systems tomarket more rapidly are usingmore high-speed interconnects. As a result, automated design tools are gaining in importance. Mezzanine systems offer another route to increasing data speeds.With tunable differential pairs, enablingmatched impedance configurations, sin gle-ended lines and power, combined with a range of stack heights and compliant-pin terminations,mezzanine connectors enable data rates up to 56Gbps, suitable for high-speed infotech and telecom applications.


demand,, driving requirements for higher speed interfaces in routers and switches, plus theth development of new interconnect technology and standards for 40Gbps and 100Gbps interfaces. Plans for 400Gbps speeds will mean no rest for connector designers, says Jairo Guerrero, director of at Molex, LLC.Here’smore onwho to tackle these chal enge s


d ivin re


wth in IP services and access speeds has led to exponentiia g owt s a


re evelopment o new f ew i s for h onnect


cess sp sp


s h s le to interfa chnology in ro


all growth in bandwidth switch , p


wth in gy and standards for 40Gbps and 100Gbps i terfaces.


Typical attachments formezzanine connectors are either press-fit or SMT. Traditionally, press-fit connectors are easier to work with, but SMT connectors offer enhanced perfo footprint optimisatio


terconnects enable high-speed data inuous growtowth in IP service


n and removing stub rmance, allowing


effect fromthe compliant pin. Recent advances, however, have reduced the performance gap to the point where the difference is null in a real channel, so when matching signal integrity, the choice of attachmentmethod can be driven by layout, routing and board thickness. Finally, employing a triad wafer design, mezzanine connectors offer the following options: high-speed differential pairs that can be tuned to 85- to-100-Ohm


impedances; single-ended triads for low- speed options; and power triads. As a result, designers need only one connector fo r different signal speeds, freeing up PCB space. As speeds increase, enhanced thermal management solutions become a key element for next generation systems. For example, stacked connectors deliver higher speed, but use around 5Wmore power - producingmore heat - in 100Gbps QSFP modules than standard interconnects. Typically, temperatures in enterprise


systemsmust bemaintained below 70°C in themodule and 45° C ambient temperatur e in the enclosure.


One successful new approach is to design in riding heat sinks and high-flow cages that optimise airmovement - potentially reducing overall temperature in an


emulated 5Woptical QSFPmodule by 9°C. Thermalmanagement strategies like this will be vital for next-generationmodules that are required to support at least 7W. As wemove into the fast-data future, new interconnect solutionsmust enable both advanced technology and increase d network bandwidth. Successful products will need to support a wide range of data rates usingmultiple connectors.


Molex


www.molex.com T: 02392 205801


www.molex.com / ELECTRONICS ELECTRONICS


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