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Battery Drain Analysis for Low Power IoT Devices

Application Notes

The Challenge

Low-power devices associated with the Internet of Things (IoT) consume power at highly variable rates, from microseconds to seconds, and from picoamperes to amperes. Accurate battery drain measurements are critical to achieving the long battery life customers expect, and Keysight’s broad range of solutions enables engineers to get convenient, fast, and accurate results that properly characterize battery drain on IoT devices.

The spectrum of design and testing needs

It is no longer sufficient for an IoT device to last a few years between battery replacements. Customers often expect 10-year battery life in many applications, and some vendors even advertise “leave for life” or “set and forget” devices that last for the application lifetime, often well beyond a decade. 

To meet these expectations, chipset designers create integrated circuits with deep sleep modes that consume very little current. These devices have operation modes with slow clock speeds, reduced instruction sets, low battery voltages, and low current consumption. These applications require testing at three to six orders of magnitude of current levels for events lasting microseconds or milliseconds.

To reduce the relatively large power consumption associated with wireless communications, standards groups are defining new low-energy operating modes that combine low radio-frequency (RF) power levels and simple connection protocols that limit active operation time. Wireless module manufacturers extend battery life by designing and testing programs for embedded processors to shorten power-hungry states.

The product designer who integrates sensing, processing, control, and communication components into a final product must know how peripherals behave and consume power. This designer has additional software or firmware control over power supplies, analog and mixed-signal components, and digital and RF subsystems. As the product goes into production, a simpler set of tests and test equipment can verify proper device operation quickly and inexpensively.

These different needs challenge the engineer to make measurements with widely varying levels of detail at each step of the development process. The chip designer and module designer need a very fast evaluation of power consumption in various device operating states. The module designer needs similarly fast measurement over many orders of magnitude on any of several chips, correlated to module firmware operations. The product designer may need slightly less precise time resolution but must know accurate overall power consumption throughout the hardware and software development process. Finally, the manufacturing test department needs to know the device operates correctly, perhaps using a simpler set of test equipment.

Wearable IoT devices

Users wear some IoT devices, such as hearing aids, digital eyewear, and fitness trackers. Because these devices are often in operational (nonsleep) modes, they tend to have shorter battery lives.

Wearable fitness devices have sensors and RF components that intermittently measure, store, and send data. To optimize the power budget and usability, the design engineer may use a variety of instruments and software to characterize energy measurements and then tune the CPU firmware to optimize the energy used during each operation. The rest of this document describes five such devices.

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