Low Power Embedded Systems Design and Power ManagementBy ZM Peterson • Feb 16, 2021
Lower power embedded systems and IoT products might have a range of power management strategies implemented at the design level, or they have some sophisticated on-chip features helping to keep power consumption low. There are also sophisticated algorithms that enable low power consumption and power management in embedded systems, and any low power system might need a combination of strategies to prevent excess battery power from being used.
If you’re designing an embedded system that must be highly power efficient while also providing the required level of computing power, there are multiple approaches you can take. It all depends on the design requirements you need to meet, followed by opting for the right low-power components where possible. After having worked on multiple low power embedded systems, I’ve compiled a few strategies we use to approach a power consumption strategy and ensure a design will have the lifetime it requires.
Low Power Embedded Systems Design Requirements
The first stage in any successful project execution is requirements gathering. For a low-power embedded system, extending battery life or ensuring overall power efficiency are likely top priorities, you’ll need to develop requirements around your need for power efficiency. You’ll need to make decisions around some of the following points:
- If your system is battery powered, how long the system will need to be deployed before requiring charging?
- How much compute resources does your system need to do its job?
- Are there power-hungry peripherals or circuit blocks that need intermittent power?
- What type of power management techniques or features can your components support?
If you have an idea of the answers to these questions, you can come up with a strategy to design low power embedded systems and low power IoT products. The design strategy starts with selecting critical components and peripherals, which may need to be paired up with a power management algorithm. Once you’ve decided on critical components, you can determine how best to implement a power management strategy at the system level.
Power consumption in an embedded system is heavily dependent on the main processor, analog front-end, and any peripherals like displays. Many processor units (MCUs, FPGAs, MPUs, etc.) and other components are specifically marketed as low-power devices, and they may enable a unique power management approach in embedded systems.
When selecting components, here are some tips you can use to design a low-power system architecture:
- Start with must-haves. Your must-have components could be a specific processor or peripheral. Start here and try to find the lowest power option that satisfies the minimum functional requirements.
- Peripheral architecture. Think about how peripheral blocks will interact with the host processor and the environment, and work these into your system architecture (see more information below).
- Interfaces and receivers. Various low-speed digital protocols (I2C, SPI, GPIO, etc.) can have different power outputs. Also, receivers and converters like ADCs could be run at lower sampling rate to reduce total power consumption.
- Components with sleep/hibernate modes. Some processors and other IC have sleep modes, where current is only supplied to critical functional blocks in the IC. Current can drop to well below 0.01 mA in these modes.
- Power regulation. Once all the important components have been selected, it’s time to think about power regulation. Aim for the highest efficiency power regulation strategy you can. Careful design of regulation stages can ensure power conversion efficiency stays well above 95%.
Power Management Techniques in Embedded Systems
Component-level power consumption is easy to address by choosing the right parts. However, there are times where a specific component that runs at high power is a must-have. At this point, the system should be designed so that certain peripherals can be toggled on and off, battery charge management is implemented, and algorithm optimization.
A strategy where peripherals are switched on/off as needed by the host controller is one way to ensure power is only being consumed when it is needed. Some components may implement this on-chip, where groups of interfaces are switched off and the core voltage is reduced to when the component is not actively processing data. This is a popular feature on many low-cost MCUs. However, at the system level, there may be system blocks that are not directly connected to the master processor. These could be switched off by simply cutting power to the peripheral block, or by putting a slave processor into sleep mode.
Power to peripherals can be managed by switching with a bus topology. Note that this might require digital/analog switch components.
This strategy is useful for multi-cell battery packs in series, but not all battery packs will support this. Implementing a battery management algorithm with a balancing system is one way to prevent excessive power from being drawn from a single cell and ensuring charge is evenly distributed across cells. One possible component for implementing a standard balancing algorithm is the BQ769x0 series from Texas Instruments. This component provides low current balancing between cells with minimal power loss in the component and microcontroller/FPGA/CPU/MPU.
Embedded systems designers should ensure any specialty algorithms in their firmware are optimized so that compute operations are minimized. Software developers working at the enterprise level often have to consider the number of logical operations involved in implementing an algorithm and need to find ways to minimize the number of operations to complete a computational task.
Firmware developers and embedded software developers need to do the same for their systems. Reducing algorithmic complexity leads to less power consumption in the host processor. By eliminating background processes and services, or by eliminating unnecessary computational operations, the processor will be performing fewer tasks while idling and will consume less power.
If your company is pushing the limits of telecom, data center, and low power embedded systems, it pays to work with an experienced electronics design firm. NWES helps private companies, aerospace OEMs, and defense primes design modern PCBs and create cutting-edge embedded technology. We've also partnered directly with EDA companies and advanced ITAR-compliant PCB manufacturers, and we'll make sure your next high speed digital system is fully manufacturable at scale. Contact NWES for a consultation.