IoT Use Cases: New Internet Connected Solutions Add Complexity to PCB Design

Applications for technologies that connect to the Internet of Things (IoT), mobile IoT (MIoT), and the Industrial Internet of Things (IIoT) have become commonplace.

Athletes—ranging from amateurs to professionals—wear wristband sensors that connect and compare heart rates, body temperature, and pace to data found in the cloud.IoT use cases also range to plants, mills, refineries, and other industries that have become safer work environments through the use of smart helmets, smart vests, and smart glasses that continuously collect health, location, environmental, and productivity data from individual employees.

In another example, intelligent sensors connected to real-time asset operations combine with online predictive analytics to monitor key assets in plants and provide early detection of problems that could cause outages. Predictive maintenance sensors detect increases in vibration, strain, and frequency. If those readings go beyond an established baseline—interaction between analytics operating in the IIoT and an Enterprise Resource Planning (ERP) system causes a notification to flow to maintenance team. The notification also includes a recommendation for the type of maintenance required to keep the system running and the timing of the maintenance.

However, the revolution doesn’t stop there. Think of smart homes, digital factories…and smart cities.

Innovation and Complexity Come Together

Those and other IoT/IIoT/MIoT-connected devices application operate through a device layer, a connectivity or edge layer, and a cloud or data center and app layer.

Low-power sensors and actuators connect to gateways through wireless networks. In turn, the gateways communicate actions that the sensors and actuators connect to the cloud through wide-area networks. The wide range of connectivity choices allow back-and-forth communication at the machine language and the transmission and reception of higher-level languages to occur.

The acquiring and transferring of data between devices and applications involves complex interactions, different frequency bandwidths, a variety of network topologies, and electronic component technologies as witnessed below:

PCB Design Begins with the Basics

With all the innovation and uses of microprocessors, intelligent sensors, DDR memory devices, and flash memory, we come back to the basic problems that plague PCB design. All the operations and communication between devices must efficiently happen without interference, crosstalk, losses, delays, impedance mismatches, or ripples at different data rates. The complexity of analog/mixed signals (AMS) requires simulation and analysis to ensure that the design matches performance requirements.

Another key point about IoT/IIoT/MIoT solutions involves antenna design. When designing your PCB, you may need to consider orientation, gain, and directivity while selecting the antenna that matches the desired form factor. For example, the Z-Wave mesh network topology used to achieve wireless connectivity for smart home products may support hundreds of devices. In another example of the impact on antenna and circuit design, Sigfox uses Ultra Narrow Band (UNB) radio technologies for radio message exchange.

Because IoT/IIoT/MIoT devices operate in multiple modes, noise becomes a larger factor. Let’s stop for a moment and consider how sensors and actuators communicate with gateways in a predictive maintenance environment. Transmission and reception between devices occurs in short bursts while the idle current and standby states last longer. Within the different operating states, electromagnetic magnetic interference emitted through the output power supply rails can degrade the accuracy needed for proper circuit operation. Along with EMI, we also must consider the impact of temperature on devices that operate in multiple modes.

As you read through the list of technologies found in the connectivity layer, most refer to low-energy consumption. While solving the basic problems associated with signal integrity, we also need to recognize the significance of low energy consumption—and power integrity--on our designs. Operations that may seem common in terms of networking such as establishing the proper network parameters and protocols become more problematic because of the required limits on energy consumption. In addition, the power supply tolerances that we build into our designs become much tighter and more precise.

Rigid-Flex PCBs and High Density Interconnects Provide Good Solutions

When considering the performance of your connected PCB design, the need for efficient form factor may require the use of rigid-flex PCBs. With the rigid-flex approach, you can eliminate connectors and connecting cables that contribute to loss, control impedance, and improve the overall signal integrity of your circuit. Rigid-flex PCBs also have less weight and more space for components.

However, as you move your PCB design concept into rigid-flex environment, you must remain aware of the transitions from rigid to flex and back to rigid. The flexible part of the circuit can interconnect circuits. Multilayer rigid-flex PCBs can also allow more circuitry within a design but can also impact your routing design. The material stresses that accompany bending a flex circuit may change your approach to trace routing, trace widths, and surface mount components. One method for distributing stress across a double-sided flexible circuit involves staggering traces and routing traces perpendicular to any bend lines.

Flexible materials are pivotal in IoT devices and wearables

High Density Interconnects (HDI) also assist with saving the space and weight for IoT-connected products. With HDI, the electrical paths become much shorter, the number of layers decrease, and the placement of components becomes more crowded. Dense trace routing yields better signal integrity and speeds signal processing.

Shorter electrical paths reduce or eliminate problems with parasitic capacitance and inductance. In addition, component placement, routing, and component connections become easier. Yet, HDI also requires greater attention to maintaining uniform traces, minimal line widths, and precise layouts.

IoT Solutions: Teamwork and SPICE Simulation

Everything involved with building an IoT, IIoT, or MIoT solution requires teamwork. Members of your design team must work together to determine design constraints and to move a design from concept to testing. Your decision to build Design-for-Test and Design-for-Manufacturability compliant boards can save time and money. Teamwork also involves working closely with fabricators and manufacturers to determine how form factor matches with consumer or industrial requirements.

Utilizing a SPICE tool early on and throughout the design and production process for an IoT device will enable you to carefully regulate your design’s production and useability.

Where limited form factors, constraints for high-speed operation, and managing output through multiple OEM factors can derail your IoT designs, utilizing proper SPICE tools will be able to minimize those issues. Proper circuit analysis can provide the security for your device’s functionality through utilizing high-level abstractions and models for accurate data, develop personalized models for parameters your device needs, and accurate mixed-signal simulation.

With most consumer electronics, you’ll also want to have an eye on manufacturability and product yield. Thankfully, SPICE simulation will be able to adjust design expectations and tolerances based on desired manufacturing yields and reliability standards. This factor will ensure your designs get out of the schematic and into the hands of your desire audience with ease and charm.

If you’re looking for circuit design and analysis that can withstand the constantly shifting demands of consumer electronics, make sure you begin your search with tools that are flexible enough to meet your needs. OrCAD PSpice will be sure to provide accurate predictions and results for your device’s production schedule.

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.