Systems and product design are serious business. The first optoelectronic system I designed was unwieldy with fibers, sensors, and electrical wiring sticking out everywhere. Sure, it got the job done but it was far from market-ready. I fondly remember when my manager compared it to the flying spaghetti monster.
If you are just beginning to delve into designing IoT products, there are many design aspects where you will need to rise to expert status. IoT devices pack mobility, low power consumption, RF communication, mixed-signal capabilities, and high-speed data transfer capabilities into a small footprint. Keeping all of these factors in mind will help you get your design correct the first time.
Industry Standards for PCBs
If you intend to eventually take your new device to market, your device will have to meet or exceed many industry standards. These standards specify several operating requirements that ensure compatibility between your device and those built by others. Getting familiar with working under industry standards early is crucial. If you can design your device to conform with standards now, it will prevent the need for a complete redesign later.
The Institute for Printed Circuits (IPC) standards are a good place to start and you will likely be referring to these standards often during the design process. Other organizations like the IEEE, ISO, and ANSI also specify operating standards for PCBs. When you begin delving into industry standards it may seem like an alphanumeric soup. No one can memorize every PCB design standard and it is important to focus on the standards that apply to your device.
IoT Applications and Low Power Design
Not all IoT devices can be plugged into the wall outlet. If your device is designed to be mobile, you should learn all you can about designing your device to use the minimum amount of power possible. Your mobile IoT device will likely run in a number of different modes, including sleep, standby, burst, etc. The best way to conserve battery power and ensure reliability in each mode is to turn off unnecessary portions of your device when they are not needed.
It is best to think about power consumption in your PCB as it occurs in different functional blocks on your board. It is a good idea to divide your PCB into functional blocks and allocate a power consumption budget for each block. It is also a good idea to consult with a component supplier if you run into power consumption issues. They may be able to recommend alternative components that use less power and help you stay within your budget.
Your IoT device will also require a memory module that will consume energy. Choosing the right memory that can meet your functional requirements can help you stay within your power budget. Each type of memory comes with its advantages and disadvantages. For example, if you choose DMA over DRAM you will gain power savings at the cost of latency and throughput. It is up to you as a designer to weigh the pros and cons of each type of memory.
Keep Your Devices Talking with RF Design
Unless you plan to have your IoT device plugged directly into an Ethernet port, your device will be connecting to the internet wirelessly via WiFi. Bluetooth capabilities may also be desirable, particularly if your device is intended to interface with your phone. Many other wireless networking protocols are used to send and receive information using RF signals. It is a good idea to familiarize yourself with the various wireless protocols if you have not already.
Link all your IoT devices with wireless communication
Governments regulate the distribution of the radio frequency spectrum, and certain frequency bands are allocated for different purposes. For example, WiFi signals operate at a 2.4 GHz frequency, and other RF protocols will operate at different frequencies in the RF spectrum. Industry standards will also specify design constraints that will help ensure your design functions properly.
Thankfully, you will not have to design your RF modules from scratch. Off-the-shelf wireless modules that already meet government regulations and industry standards can be purchased from electronics suppliers and can be easily incorporated into your design. These parts can help you keep your form factor small while still including all the functionality you need.
Many IoT devices, especially mobile phones and devices for smart homes, will operate using a number of sensors that allow the device to interact with the world around them. Sensors in IoT devices output analog signals that must be converted to digital signals. Once converted to a digital signal, the digital data can be encoded and manipulated just like any other set of digital data.
Due to the ever-increasing amount of data being processed by IoT devices, processors must move data between components at higher speeds. Your layout will need to take into account issues like crosstalk, clock skew, propagation delay, attenuation, and impedance matching. Mixing high-speed digital and analog signaling also requires that the analog and digital portions of the board be segregated in different parts of the board.
With proper simulation protocols in place, you can be sure to have accuracy in IC and behavioral construct macro modeling. Ensure that your PCBs are secure with a strong SPICE simulator.
Simulation, Smaller Boards, Higher Component Density
When you’re already tasked with obeying the power demands and mixed-signal protocols, like packing all the RF modules, logic ICs, power management components, microprocessor, traces, memory, displays, charging/USB port, and other electronic components, it can feel like a game of Tetris. Every inch of real estate is precious, and you’ll want to make the best use of all of it if you want to get the most out of your device.
Arranging your electronic components can feel like a game of Tetris
Fortunately, you don’t need to manage each individual factor alone. With proper SPICE simulation, you’ll be able to keep track of power efficiencies, design vulnerabilities, analyze for impedance and determine necessary form factor limitations. A significant boon for your analysis, SPICE libraries will have easy-to-access component parameter integration and modeling, as well as templates to build custom models from.
When you’re working through your IoT designs, the last thing you want is for your design and analysis to be less than stable. Whether you’re facing difficult power demands for your sensor device, or working through tricky form factor limitations, OrCAD’s PSpice simulator is capable to provide the best results for you.
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