The chips are down for chip down design in small to medium volume applications

By Harvey Wilson   |   September 16, 2024   |   Provided By Avnet Silica

When designing a new microcontroller-based product, there are two basic approaches: a chip-down approach, where a custom PCB (printed circuit board) is designed using chip-level components, or a modular approach, where pre-designed modules are used to implement the required functionality.

The chip-down approach is not suitable for all companies or all products — it's costly, risky, and time-consuming. Smaller companies may not have a design team with the diverse technical skills required. With the availability of SoM (system on module) products from companies like Arduino, you have the option of a cheaper, simpler, and faster design process.

This article will compare the two approaches and show why module-based design is the best solution for the majority of small and medium volume applications.

Chip-down versus module-based approach

Chip-down design involves selecting every component, designing a PCB, committing to manufacture, and then testing and certifying the design. One or more of these steps may need to be repeated as a result of testing or changes to requirements.

This is a time-consuming and expensive process that is most suitable for products sold in large quantities, typically more than 50,000 units annually. It involves a huge investment of time and resources but can cut the manufacturing costs of the product. This is, therefore, a good approach for large companies producing high-volume products where shaving a few dollars off the unit cost can make a considerable difference to overall revenue.

The alternative is to take advantage of the wide range of off-the-shelf modules that provide the functions required for your product. The modules available include microcontrollers with peripherals and I/O, as well as add-on modules that implement specific functionality, such as sensors, cameras, and communication interfaces.

These components are ready to go, with firmware, middleware libraries, development tools, tutorials, and other supporting software provided. There is also an active community of open-source developers, and their collective experience and knowledge can speed up your own development by providing examples, advice, and support.

Some of the trade-offs to be considered are:

• Design time and expertise required
• Non-recurring engineering (NRE) costs
• Certification cost and time
• Production cost (per unit)
• Physical size

These are discussed in more detail below.

Advantages of module-based design

If we consider development time, a chip-down design may take months of work, possibly needing specialist skills, like RF design for wireless connectivity. More time is then required for prototype production and, typically, the design will need to be iterated at least once before it’s ready for production. 

A module-based system can be assembled and working within days. Not only is the hardware integration simpler, but software development is eased too. For example, transferring data to a Bluetooth or Wi-Fi module over a standard interface such as I2C, is far less complex than having to worry about the low-level details of programming a radio chip. This means that your engineering team can focus on developing innovative products, rather than worrying about low-level functionality.

If your product includes wireless connectivity such as Bluetooth, Wi-Fi, or cellular, then the product will need further testing and certification to ensure it meets FCC and other standards. This can take months and is very costly. There is also the risk that it may result in further design changes, adding more cost and delay.

Using a pre-designed and pre-certified module greatly simplifies certification of the product. It becomes a routine process that can be done by a certified test lab in a week or so.

Overall, using a module-based approach can result in a 20–50% reduction in development time and a corresponding cost saving. You can also gain up to two years early revenue by getting your product out sooner.

Chip-down design

There are a couple of areas where the chip-down approach wins, if sales volumes justify it.

One is the bill of materials (BoM) cost for manufacturing the product — the cost of the bare chips used to implement a function is less than the price of the equivalent module. However, it may take two years of production to recover the initial NRE costs. You may need to commit to a large capital outlay — for example, some of the components will only be available (or: available at a reasonable price) in quantities of tens of thousands. You may also be exposed to single-source and related supply chain risks.

Secondly, if the physical size of the product is a constraint, then a fully custom design can be smaller or made to fit a specific form factor.

But even if the potential volume for your product is large enough to justify a chip-down design, it may make sense to test the market first with a product that costs less to design and can get to market quicker. If the product is successful, the NRE costs of a chip-down design can be justified. 

The module-based system can also be used as the basis of the later chip-down design, eliminating some of the test and debugging time that would otherwise be required.

Examples of SoM products

The Arduino PRO range is designed for enterprise applications including industrial control, AI edge processing, and robotics. It preserves the same ease of use of the classic Arduino products, enabling rapid development and deployment, while providing extended temperature range, greater robustness, and conforming to industrial standards.

The Arduino PRO range includes the Nicla family of industrial-grade sensor modules. These can operate as autonomous, battery-powered systems, with enough compute to support real-time processing of sensor data to enable continuous environment monitoring. Their small-size means they can be integrated into existing hardware platforms. Wireless connectivity, through Bluetooth or Wi-Fi, also allows them to be used as part of a wider sensor network.

The Nicla range includes:

• The Nicla Sense ME is a wide spectrum Motion and Environmental sensor. This has 4 low-power industrial-grade Bosch sensors with microcontrollers to provide powerful data fusion capabilities on the edge. It can accurately measure rotation, acceleration, pressure, humidity, temperature, air quality, and CO2 levels. It includes Bluetooth LE for wireless connectivity.
• Nicla Vision is a ready-to-use, standalone camera for machine vision applications. Dual-core processor provides compute for analysing and processing images on the edge using machine learning. It includes a 2 MP colour camera, smart 6-axis motion sensor, integrated microphone and distance sensor, plus it’s suitable for asset tracking, object recognition, and predictive maintenance. It has integrated Wi-Fi and Bluetooth LE connectivity.

These are complemented by the Portenta compute modules that can run powerful AI algorithms and machine learning on the edge. 

To get the best combination of features for each module, at the best price, the Arduino PRO modules use a variety of microcontrollers from STMicroelectronics, NXP, and Renesas. The Arduino middleware means you can run the same software on all these different vendors’ silicon. This makes it easy to switch modules as your requirements change, and reduces single-source and supply chain risks.

To complete the offering, Arduino Cloud is an all-in-one IoT platform that lets you visualise and control your connected projects remotely.

Conclusions

The main advantages of the modular approach are:

• Development time: By using a module-based approach, you can prototype your system in days. This means reduced time to market and time to revenue. 
• Flexibility: A wide range of standard modules make it easy to integrate the sensor and connectivity functions you need.
• Risk reduction: As well as being ready to use, the module manufacturer also takes care of component selection and compatibility testing, which minimises production and supply chain risks.
• Access to expertise: Instead of needing in-house engineers with detailed knowledge of technologies — such as kernel device drivers for the operating system, RF board design, and wireless communication standards — you can use modules created by those with the necessary expertise.
• Innovation: The module manufacturers take care of the detailed hardware and low-level firmware, leaving you free to focus on developing your product. 

In today’s fast-moving world, the ability to rapidly change to meet new markets is key to developing a successful product. Any delays can mean lost revenue or even losing the market to a competitor. The timescales for a full custom chip-down design limit the agility and responsiveness that is a key advantage of smaller companies.

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Harvey Wilson

Harvey Wilson is a Systems Engineer Professional (Smart Industry) for Avnet Silica in the EMEA regio...

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