How to make your embedded system design more resilient in the face of supply-chain disruption

By Yves Grillet
Vertical Segment Manager Europe (Embedded Solutions), Future Electronics

Manufacturers of embedded systems have long known about the benefits and trade-offs of basing designs either on discrete microprocessor components or on a ready-made system-on-module (SOM). This is often referred to as the ‘Make or Buy?’ dilemma: buying in a complete modular solution, which provides the microprocessor with its supporting components, such as memory and a power management system, on a single compact PCB saves a substantial amount of development time. It frees specialist digital designers to work on the differentiated elements of a product design. 

But a modular solution’s bill-of-materials cost is often higher than that of the equivalent discrete components. In addition, when using discrete components the designer has the freedom to make the design in any form factor, or with any non-standard component or technology elements. 

These arguments are well understood by OEMs, but a new factor affecting the choice is perhaps less well understood: the benefits of designing for resilience. 

The problems which plagued the car industry in 2021-22 show how much economic damage can follow from severe disruption in the semiconductor supply chain. When a design is reliant on a single source of a key component that is not easily substituted, the production line is then at the mercy of that component’s supply chain: it is the product’s weakest link in the chain. 

So do embedded system manufacturers need to be thinking more deeply about how their choice of the key processor component affects the resilience of their production system? 

 

The causes of volatility in the semiconductor supply chain 

The microprocessor is the key point of vulnerability in an embedded device OEM’s supply chain because of the advanced technology on which it is based. Embedded systems that run on a Linux® or Android™ operating system require high-performance processors that use the latest packaging, high-speed interface and DRAM memory technologies. 

This means that every microprocessor family is a unique part based on proprietary technology, and has a single source. In many cases, the microprocessor is also supported by dedicated companion chips such as a power management IC (PMIC), which will also usually be a single-source part. 

The supply of any of these single-source parts can be subject to disruption due to various causes: the COVID-19 pandemic, interrupted transport links, international trade disputes and sanctions, and natural disasters such as earthquakes or volcanoes can halt shipments of a microprocessor or its PMIC. Component shortages or extended lead times can also hamper a factory’s ability to maintain normal production operation. 

If this happens, it is not easy for the OEM to quickly implement a plan B: substituting a different microprocessor for the original microprocessor is difficult, and takes considerable development effort and time. The same applies to the device’s companion PMIC. Because the PMIC provides the specific mix of power rails required by a specific microprocessor, it cannot simply be replaced by another part. Each PMIC also requires its own software driver running on the microprocessor to manage the power rails, optimize the PMIC’s power consumption, and control sequencing and other device-specific operations. A replacement PMIC requires a new software driver as well as a new hardware layout. 

Disruption to the supply chain of either the microprocessor or the PMIC will, in many cases, cause an embedded system OEM’s production line to be halted, resulting in substantial economic losses. 

This has an important bearing on the Make or Buy decision, because the use of a SOM helps to insulate the OEM from supply chain disruption. 

 

Avoiding development risk

In addition to the supply-chain risk to which embedded system OEMs are exposed, development risk arises from the technical challenge of implementing a microprocessor-based design. This risk comes from two key elements of the design: 

• The small pitch of the BGA package calls for specialist layout expertise to design the fan-out from the microprocessor. The package also calls for the use of special production machinery and a high-cost PCB with at least four layers 
• High-speed bus interfaces and high-speed DRAMs both require expert design capabilities 

Dedicated CAD tools are used to configure the track timing, impedance, isolation characteristics, and shape of the PCB routing to be compatible with the tolerances specified by the IC manufacturer. There is a substantial cost to this part of the development effort, both in terms of engineering time, and for acquisition of the CAD tools. 

If the OEM decides to make rather than buy, then, it is exposed to the risk of a single source of supply, alongside the requirement to manage dedicated engineering teams, and undertake a long and complex development process. Even when a development is completed, the OEM must install advanced production equipment and processes to manufacture a high-cost PCB. 

 

SOM: offloading the supply-chain and other risks

The OEM which chooses the buy rather than make option shifts these risks on to the provider of the SOM: the SOM manufacturer will handle all the complex issues involved in development of the microprocessor sub-system, maintaining it over time, porting the design to new versions of the chip’s software development kit (SDK), implementing chip upgrades, and managing a device’s end-of-life (EOL). 

In return for the premium paid via the SOM’s higher unit cost, the OEM gains several valuable benefits: 

• Product designers can concentrate on unique features which provide its added value
• A SOM is provided in a standard form factor. This means that if the supply of a SOM from one manufacturer fails, it can be replaced by a SOM from a different manufacturer that features the same microprocessor
• A SOM’s standard footprint also enables the OEM to migrate a design from one generation of a microprocessor family to the next without redesigning the end product’s hardware. This capability also supports the development of a family of end product designs with low-end, mid-range and high-end capabilities based on a family of microprocessor parts
• Use of a SOM dramatically shortens development time and can result in faster time-to-market 
• The simpler and quicker development process when using a SOM also gives the OEM more freedom to experiment with new design concepts and advanced technologies 

 

New smaller form factors heighten appeal of SOMs

To make SOMs from different providers interchangeable, the industry has developed a range of standard form factors for SOMs. Now a recently introduced standard gives OEMs the opportunity to develop more compact product designs. 

Fig. 1: The OSM standard offers much higher pin density than the earlier SMARC and Qseven standards for embedded computing modules

The new Open Standard Modules™ (OSM) form factor, sget.org/standards/osm, was developed under the aegis of SGeT, the Standardization Group For Embedded Technologies. SGeT is known for its development of the earlier Smarc and Qseven standards. It developed the new OSM standard to provide a number of benefits: 

• Increase I/O density, as shown in Figure 1
• Meet demand for smaller, lower-cost embedded computer modules 
• Provide a module in a package which can be soldered to the PCB, to avoid the use of connectors. A 1.25 mm ball pitch also helps to make the hardware design more robust 
• Offer pin-compatible options for swapping between different IC manufacturers and different Arm® processor or microcontroller architectures
• Support the development of product families with different I/O options via the provision of four pin-compatible form factors. This eliminates the need to redesign a product’s carrier board for each new variant of an end product design

OSM modules are available in four different form factors, as shown in Figure 2. 

Fig. 2: The dimensions of the four standard OSM form factors. (Image credit: iWave Systems Technologies)

Already, these form factor options are well supported by commercial suppliers of OSM modules. For instance, iWave supplies OSM modules featuring microprocessors from NXP Semiconductors, Renesas and STMicroelectronics, as shown in Figure 3. 

 

iWave Part Number	Processor Manufacturer	OSM Size	SOM Key Features
iW-G40M- OLPQ-4L002G-E016G-BIA	NXP	Large	i.MX8M Plus Quad OSM SOM with 2 Gbytes LPDDR4, 16 Gbytes eMMC, 802.11ac Wi-Fi plus Bluetooth 5.0
iW-G46M-OSXD-4L002G-E008G-BIA	NXP	Small	i.MX 8XLite Dual, 2 Gbytes LPDDR4, 8 Gbytes eMMC
iW-G50M- OL93-4L002G-E016G-BIA-PP	NXP	Large	i.MX9352 Dual, 2 Gbytes LPDDR4, 16 Gbytes eMMC with Wi-Fi, Bluetooth
iW-G53M-OM2U-4L002G-E016G-BIA	Renesas	Medium	RZ/G2UL CPU, 2 Gbytes LPDDR4, 16 Gbytes eMMC
iW-G53M-OM3U-4L002G-E016G-BIA	Renesas	Medium	RZ/A3UL CPU, 2 Gbytes LPDDR4, 16 Gbytes eMMC
iW-G53M-OMFV-4L002G-E016G-BIA	Renesas	Medium	RZ/Five CPU, 2 Gbytes LPDDR4, 16 Gbytes eMMC
iW-G54M-O033-3D512M-Q002M-BIA-PP	STMicroelectronics	Zero	STM32MP133 CPU, 512 Mbytes DDR3L, 2 Mbytes QSPI Flash

Fig. 3: OSM modules available from SOM manufacturer iWave

 

When Future Electronics supplies an iWave OSM module to an embedded system OEM, it can also provide a rich choice of supporting technologies, including a single-board computer for application porting and testing, and associated components such as: 

• Camera modules
• TFT displays
• Enclosures
• Heat-sinks 
• Wi-Fi^® and Bluetooth^® wireless modules
• GNSS satellite positioning sensors
• LTE and other wireless communications modules

iWave SOMs are also supported by the microprocessor manufacturer’s software offerings, such as artificial intelligence and machine learning libraries and a Linux or Android SDK. 

 

Conclusion

By using an OSM embedded computer module, which has a standard footprint, I/O provision, functions and pin locations, design engineers can base multiple product designs on a single carrier board while retaining the ability to switch from one MPU to another, as shown in Figure 4. 

This minimizes the OEM’s exposure to supply-chain risk, and makes a design resilient: with a SOM, the OEM can replace a microprocessor which is unavailable or on allocation with a different microprocessor, without the need for a hardware redesign.  

Because the OSM standard is available in four standard footprints, the OEM can build a product family with feature sets ranging from simple and basic with the Zero OSM option, up to a highly integrated, high-performance unit based on a Large OSM module, capable of offering a high number of I/Os, and supporting advanced capabilities such as Wi-Fi and Bluetooth wireless communication, high-speed cameras, AI functions and a large, high-performance display. 

Fig. 4: An iWave single-board computer that features various OSM SOMs: the ITX SBC iW-RainboW-G40S (top), and the ITX SBC iW-RainboW-G50S (bottom). (Image credit: iWave Systems Technologies)

 

Specifications of the iWave SBC featured in Figure 4:

• Rainbow G40S featuring an I.MX8M Plus Quad microprocessor SOM
• Part number: iW-G40D- OLPQ-4L002G-E016G-BIA
• Key features: i.MX8M Plus Quad, 2 Gbytes of LPDDR4 DRAM, 16 Gbytes eMMC, Wi-Fi and Bluetooth connectivity, operating-temperature range -40°C to 85°C 

 

• Rainbow G50S featuring an i.MX9352 microprocessor SOM
• Part number: iW-G50S-OL93-4L001G-E008G-BIA-PP
• Key features: i.MX9352 Dual, 1 Gbyte of LPDDR4 DRAM, 8 Gbytes eMMC, Wi-Fi and Bluetooth connectivity, operating-temperature range -40°C to 85°C