Low Power Design Basics

Created: 08/21/2020


Low power means average power consumption in usage of the electronic product is at its minimal via low power design techniques in both hardware and software level respectively.

The benefit of low power can be broken down in two parts:

Lastly, the often overlooked area for low power design is carbon footprint due to carbon emissions. This reason is that carbon dioxide generation is directly proportional to energy consumption originated from power plants by burning fuel or coal to generate that electricity.

One might dismiss this statement initially and have a hunch that it is unrealistic for consumer electronics to have a such significant impact on carbon emissions, but what if I tell you that 250,000 equivalent of car emissions per year can be saved if we reduce idle screen on time from 4 hours to half of an hour for just one year of TV roughly in tens of millions range? You might be surprised to learn that, and so was I when I first worked on it collaboratively with a hardware sustainability team. We did a power consumption impact of TVs on carbon emission study. As a result, the lesson to learn here is that large scale and always powered-on consumption electronics can make a significant impact in sustainability in carbon footprints.

The true goal of this article is to educate system EE, system architects, and systems engineers to be aware of their carbon footprint impact and while providing technical guidance/ideas to how to tackle this problem.


Power states: This denotes various power consumption levels: active, idle, suspend, and off,  that the device enters under different uses.

Connectivity: This is related to wireless and/or wired interoperability capability with other connected devices within the network.

System on Chip (SoC): This is a heterogeneous multi function chip that embeds a generous purpose processor with special purpose processor along with internal memories and peripheral controllers to simplify hardware design. 


At a higher level, low power design is achieved by specialization and division of computation tasks to dedicated hardware blocks, which is controlled by the power management unit (PMU) and resource scheduler of an operating system. 

This might sound confusing at first; however, if we take a step back and examine the underlying reasons that a factory is efficient at producing goods, one can see that specialization and division of labor improves efficiency in resource allocation and execution. Similarly, in electronics design, "specialization" is achieved by using special purpose processors or commonly system on chip (SoC) which consists of special purpose processor such as graphic processor unit (GPU), audio processor (aDSP), power management unit (PMU), sensor fusion hub, radio modem, etc. Lastly, division of tasks is achieved by offloading tasks to these special purpose processors by software level controls. As a result, efficient low power design is achieved.


Software level: Optimization made using controls from software systems.

TV Low Power Design:

With power states in mind, the general power number for most common 4k 55-inch TV is 100W in active, 10W in idle, 0.3W in Suspend, and 0 W in off. This implies the most power saving technique is to minimize all possible active states and transition to idle or suspend power state whenever one can without impacting user experience.

Depending on the product requirements, a general approach is having a timer that turns the TV from active mode to idle mode after idling for 15 mins and turn TV from idle state to suspend after an additional 30 mins. If the TV requires voice activation, then special audio hardware such as a wake word digital signal processor is needed to keep voice detection active while keeping the rest of TV hardware off to achieve suspended power state. We call this technique offloading, and it's widely used.

Low Power Sensor Design:

Sensors provide constant streams of information updating the state of electrical devices with information like temperature, motion, object orientation, etc. These constant streams of data are fed into sensor fusion cores for data processing and event detection such as the step counter of a fitness watch. A general approach for low power design is using an always-on low-power microcontroller (We generally refer to this processor as sensor hub) to offload event detection from the main application processor.

In practice, this sensor hub processor is either embedded in the System on Chip or acts as a standalone microcontroller which supplements the main processor.

Bluetooth Connectivity Low Power Design:

Hardware Level: Optimization made using controls from the hardware system.

Power Electronics Design:

Clock Source:

Summary & Conclusion:

Low power design is very crucial to meet today's consumer demand due to miniaturization and portability of hardware products. The main challenge is for the device to stay connected while maintaining an extended period of usage time. As a system level engineer, both hardware and software level designs must be considered to meet the user's wants and needs.