32 Bit Microcontroller: A Beginner’s Guide

September 17, 2020 Cadence PCB Solutions

Key Takeaways

  • Learn the basics of 32-bit microcontrollers.

  • Find out when you should use a 32-bit microcontroller.

  • Explore circuit design tips for 32-bit microcontrollers.

I failed to understand how Dyson vacuums had such a strong group of loyal followers. I wasn’t convinced that it was a superior vacuum until I bought one for myself. To my surprise, this powerful vacuum leaves the floor spotless with a single pass, and I immediately became a loyal follower. My old vacuum, which cost a fraction of a Dyson, took multiple passes to deliver the same result.

My degree of amazement over my first Dyson vacuum is similar to my degree of amazement at the performance of 32-bit microcontrollers. After working on various projects with its 8-bit counterpart, I was assigned to a project that tapped the full power of a 32-bit microcontroller. As an embedded design engineer, it put me in a different world.

What Is a 32-Bit Microcontroller?

Human hand holding a printed circuit board with 32-bit microcontroller

32-bit microcontrollers are rich with I/Os and peripheral interfaces.

You probably already know that a microcontroller is a piece of a semiconductor chip that does arithmetic processing and controls the circuit through the I/O and peripheral interface. The name ‘32-bit microcontroller’ implies that the microcontroller is capable of handling arithmetic operation for a 32-bit value. Compared to an 8-bit microcontroller, the 32-bit microcontroller takes fewer instruction cycles to execute a function due to its wider data bus. 

With its superior performance, a 32-bit microcontroller is often built with more peripherals and memory. For example, the NXP LPC1700 series features 4 32 bit timers, SD/MMC, USB, Ethernet Mac, CAN, and other peripherals, which is not possible with an 8-bit MCU.

While they boast powerful performance and are rich in peripherals, 32-bit microcontrollers are power-hungry components. They operate at higher frequencies that range between tens to hundreds of Mhz.

When Should You Use a 32-Bit Microcontroller?

Biometric scanning device powered by 32-bit microcontroller

32-bit microcontrollers provide the needed-power for biometric scanning devices.

Unlike a Dyson vacuum, a 32-bit microcontroller isn’t your go-to solution for every project. First of all, it is more expensive than the 8-bit MCU. In some designs, using a 32-bit microcontroller is deemed overkill and introduces unnecessary cost to the design. 

32-bit microcontrollers are also a bad fit for battery-operated circuits, such as wireless IoT sensors. They would quickly drain the battery even when operating at the slowest clock rate. 

32-bit microcontrollers are a great choice in these circumstances:

  • When you need a microcontroller capable of handling intense data processing. For example, a biometric controller that compares a fingerprint with tens of thousands of records and responds in a split second.

  • When you have a complex circuit in need of a microcontroller that can handle multiple peripherals. In such cases, it is more economical to use a 32-bit microcontroller than using a few logic ICs in the circuit.

  • When the code size of the program is too large for an 8-bit microcontroller. 32-bit microcontrollers are built with larger flash memory. 

Circuit Design Tips for 32-bit Microcontrollers

32-bit microcontroller power supply with large heatsinks

Ensure the power delivered is stable and sufficient for the microcontroller.

As a PCB designer, your skill is tested to the limit when working on a 32-bit microcontroller. You’re dealing with a higher pin-count, finer pitch component that’s likely to operate at high speeds. This means that mistakes will be more pronounced, as the microcontroller’s stability and functionality will be compromised.

Therefore, pay attention to these specific areas when you’re designing with a 32-bit microcontroller:

Power Supply 

32-bit microcontrollers demand clean and stable voltage. They are typically running on 3.3V or 1.8V, which means there’s very little room for fluctuation. The power delivery network needs to be carefully designed with proper separation between analog and digital supply rails.

Ground separation and return path considerations are also equally important to ensure the microcontroller’s operation is not disrupted by unstable supply voltage. Noise introduced into the voltage supply trace can cause erratic behavior, such as inaccurate ADC readings or causing the MCU to randomly reset. 

EMI 

It’s easy to mess up a 32-bit microcontroller design if you ignore best practices for EMI mitigation. When operated at high speed, the microcontroller can be a source of EMI as well as be on the receiving end of external interference.

Separating high-speed traces from analog signals, using proper grounding techniques, short return paths, and keeping the length of different traces equal are some ways to prevent EMI issues on your PCB. 

Thermal Dissipation 

When the microcontroller is operated at higher speed and/or with more peripherals activated, it can generate significantly more heat. Therefore, you’ll need to ensure that the heat is properly dissipated, particularly if the PCB is placed in an enclosure. 

To ensure that your 32-bit microcontroller functions optimally you will need a PCB design and analysis software package that allows you to set tight design constraints. OrCAD PCB designer, by Cadence, allows you to navigate through these challenges by setting and visualizing constraints in real-time, as well as saving constraints for future projects to avoid starting from scratch. 

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

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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