Get up to speed with backplane evolution

Understanding how backplane technology has evolved can help purchasers support high-speed data transfer, without increasing costs. Schroff’s Marc Caiola explains

The mechanical framework of an electronics packaging system is provided by the enclosure, including mounting boards

High-performing network equipment is crucial to ensuring continuous access to information and communications platforms. Backplanes are at the heart of this functionality, with responsibility for data traffic and supplying power to individual function boards managing large volumes of data. To properly maintain a high-functioning network, it is essential to understand the design and functionality of the backplane.

With current trends moving towards multi-core processors and the increased processing power of bus systems, backplanes are expected to reach consistently new performance heights. To accommodate these changes, backplane technology has evolved, delivering high-speed options capable of meeting next-generation data transfer, without increasing costs.

Understanding architecture

The architecture of the backplane is determined by the type of data transmission required, either parallel or serial, and the bus system, such as VMEbus, CompactPCI, MicroTCA or AdvancedTCA. In an electronics packaging system, the mechanical framework is provided by the enclosure, including the mounting of the boards. Traditionally, these boards were electronically connected to one another via cables, but today, these cables are typically contained on PCB boards situated near the rear of the system, or in the center when a rear I/O board cage is added. These wiring backplanes provide the necessary electrical connections to direct data transmitted between boards via a data bus and deliver power to the individual function boards.

In the past, backplane supply voltage was typically five volts DC, while today’s boards are often supplied at 12V, with the lower voltages for logic components being derived from this on-board. A reason for this change is to accommodate the supply voltages for processors and controllers, which vary considerably and are generally very low. With entire copper layers integrated into the backplane for the main supply voltages, these solutions are constructed to minimise interference and ensure high current capacity.

In addition to its electrical functions, the backplane adds an important element of mechanical stability to the system. Currently, backplanes may contain from four to over 30 layers and have a thickness of 2.4 to 8.0mm or more. Bolting the backplane to at least every other slot increases construction strength.

Wiring backplanes provide transmit data between boards and deliver power to individual function boards

Delivering on data

Early backplanes only needed one data line between communication partners, but due to the ever-expanding data volumes exchanged between boards, this is no longer sufficient. Connecting multiple lines in a parallel bus allows several bits to be transmitted simultaneously. With this configuration, the number of parallel lines can be endlessly increased to eliminate limits on data transfer. This also means however, that the number of pins on the connector must be continually increased or the transmission rate must be increased, resulting in physical space constraints and synchronization issues for data being sent or received.

Alternatively, it is possible to utilise a serial data transmission process in which each bit is sent in succession through a single transmission line. This is compatible with multiple topographies, such as dual star, full-mesh, replicated mesh and daisy chain, providing greater performance flexibility. For instance, dual star provides a failure safety feature, with a second redundant switch taking over from the first in the event of any malfunction. Alternatively, the second switch can be used to double the transfer rate. By using a full-mesh topography with AdvancedTCA, each board is connected through four data ports. While this method eliminates the need for a star point between sender and receiver, it does require a considerable number of lines. Configurations such as replication mesh and daisy chain are all designed to provide faster data transmission and reliable performance.

Cost-effective design

The arrival of PCI Express, Gigabit Ethernet and Serial Rapid I/O has elevated the need for high-speed backplanes, but users also want to remain cost-effective. Advanced high-speed backplanes can operate at 40G and some are even manufactured with improved FR4 material to support networking needs without increasing costs. By combining cost-efficiency with signal integrity, these backplanes offer faster point-to-point connection between boards for enhanced internal and external communications.

Due to the number of configurations with serial data transfer such as CompactPCI Plus, MicroTCA and AdvancedTCA, modern backplane manufacturing also supports enhanced customization capabilities. There are advantages to using a complete system provider, with all components, including the backplane, matched to the system.

Looking ahead, backplane technology will continue to accommodate rising processing power and networking demands. This will ensure that crucial data is transferred faster, but also maintain reliable data traffic patterns and deliver the necessary power distribution to networking boards.