"Chipping" Away at the Embedded Form Factor

Cheap processor intelligence is being built into virtually every controller chip released today—chips which are no larger than a thumbnail! This runs the gamut from sensors to communication chips to A/D and D/A chips to power chips to microcontrollers. Yesterday’s 12" x 12" controller board, multi-card backplane system, or three-card stack has been shrunk into single chip solutions with USB, I2C, or SPI output! The result...appropriate board level form factors must be re-thought.

Scaling down form factor footprint sounds easy enough, right? While smaller semiconductors encourage smaller form factors for embedded applications, the success of a form factor resides in having sufficient space for appropriately defined connectors. Connectors have become, for lack of a better word, the "bottle neck" to shrinking form factors. "Connectorology" is the key to shrinking form factors appropriately for embedded OEM users.

The study of connectors and their mix of protocols, aptly coined "connectorology," ensures OEMs maximize their efficiency and effectiveness. For example, a "thumbnail" SOC chip offers several system level protocols users might want to implement in their embedded application. To alleviate the burden on the OEM, board level manufacturers are challenged with supplying a connector to facilitate access to these protocols. Typically there are three approaches to choosing a connector.

One way is to bring out each protocol supported by the CPU or SOC chip to individual connectors. This approach typically works well for what is commonly called a "reference design" board. The board size is defined by the number of connectors required to communicate with all of the I/O options from the chip. This board typically falls short of the needs of OEM users because the board is maximized for the chip’s performance with little regard to the needs of an embedded system. In this case, all types of I/O are equal and have an equal position on the board which enlarges the physical dimensions of the boards not to mention adds costs for multiple connectors (see Figure 1).

Figure 1

The second approach is for the board level manufacturer to randomly "stuff" several protocols into a compact connector coming off the board with hopes that it meets the user’s needs. While this approach is easy for the board level manufacturer and appears at first glance to meet the need for smaller footprints, it shifts a significant burden and cost to the user and adds bulk in unsuspected places. Users find they need to purchase a customized "breakout" board to gain access to the protocols or signals from the connector. In the end what was saved on an "inexpensive" single board computer is spent in custom cabling and mounting hardware (see Figure 2) needed to access the I/O—a cost easily overlooked in planning a system.

Figure 2

Embedded OEM users often find board-to-board communication the most cost effective and efficient value for their system. The best approach to choosing a board-to-board connector scheme is to evaluate the I/O and communication protocols required by the system, plus the power, reliability and energy demands, not to mention the overall assembly environment and budget for the end product. A complete system approach emphasizes the value of selecting a popular, industry-supported board-to-board stacking standard which clearly defines the appropriate mix of protocols for the system. This ensures that the user does not have more cost or complexity than he or she needs burdening one’s system on multiple levels including form factor size. It also ensures that the user does have what he or she needs and therefore doesn’t have to add expensive, bulky cables or breakout boards. A well-defined connector specifying pre-defined protocols enables OEM users to gain valuable access to common add-on I/O devices in the most efficient and effective space; the best example of this is StackableUSB™ (see Figure 3).

Figure 3



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