Insights > Benchtop

Enhance the Battery Life of Your Wireless Devices

2020-11-26  |  9 min read 

Introduction

As more portable electronic devices with multiple features hit the market, battery run time becomes critical for product differentiation and customer satisfaction. Consumers frequently expect long battery life for their applications and devices. The insatiable demand for anytime, anywhere access leads to end-user expectations that increase the pressure on product designers to design battery efficient products.


Battery life is critical to end users since a long battery life is a major differentiator in consumer buying decisions. Devices with a short battery life can damage a company’s brand, lead to decreased sales, and even cause a costly recall. Replacing batteries often costs more than the mobile device.

This blog talks about using subcircuits to reduce overall power consumption to maximize the device’s battery life.

Scaling the measurement challenge
To maximize battery life, you may use a variety of advanced power management techniques. For example, subcircuits can rapidly turn on and off to help reduce overall power consumption. As the device transitions between different operating states, dynamic current consumption ranges from sub-microamperes to amperes.

Measuring dynamic changes is essential to understanding power consumption and battery life. However, handling a 1,000,000 to 1 ratio between minimum and maximum current levels is impossible with typical tools like digital multimeters (DMMs), oscilloscopes, current probes, and conventional source / measure units (SMUs), or multiple shunt resistors. Using these tools can result in poor results, inaccurate interpretation, and daily challenges.

Traditional measurement methods

Current probe and scope: This process is the simplest way to measure dynamic current waveforms and offers a suitable measurement range, wide bandwidth, and time correlation of events. However, there are three key problems:

  • accuracy depends on the scope’s resolution
  • dynamic range reaches down to just a few milliamps and
  • periodic zero compensation needed

DMM with auto-ranging: The methods used in most DMMs can measure a wide range of current levels. However, most DMMs designed for low frequencies cannot handle the pulsed currents found in battery-powered devices. Because ranging can take several milliseconds, the DMM may miss part of the current waveform. Worse yet, the input impedance may change during auto-ranging, and this can make the device under test (DUT) lock up or shut down.

Precision shunts with a DMM: These offer good accuracy at any level and are used to get milliamp-level readings. However, different shunts are necessary to measure various levels — resistance must be high for low currents and low for high currents. Shunts can add a burden voltage that may affect the measurement results.

Conventional SMUs: With measurements into the picoamp range, these are perhaps the most accurate way to measure steady currents. However, the coupling between the output source and measurement subsystem may change the output current limit, including glitches or voltage drops during range changes that can interrupt test and damage DUTs.

New Measurement Methods
The Keysight N6781A and N6785A two-quadrant SMU modules plug into Keysight’s N6705C DC power analyzer mainframe to provides high accuracy and flexible measurement capabilities to overcome these measurement challenges. The N6781A and N6785A two-quadrant SMU provides stable DC output voltage, programmable output resistance, and an auxiliary digital voltage meter (DVM). Combining these solutions will enhance the battery life of your devices.

Seamless measurement ranging: This patented capability enables you to measure and visualize the current drain in new and informative ways. A single sweep provides accurate measurements that range from sub-microamps to amps.

Current only measurements (ammeter mode): This mode enables you to connect a battery to the DUT to simultaneously log the current drain profile and battery voltage values with no shunt burden voltage.

Fast response DC source: The N6781A and N6785A two-quadrant SMU modules provide fast recovery times and glitch-free operation when powering dynamic loads. The absence of unexpected output glitches helps ensure the proper operation of the DUT.

Battery emulator mode: The source is programmable in terms of DC level and output resistance. This capability helps you to emulate a battery accurately.

Precision constant current or constant voltage load: The N6781A and N6785A two-quadrant SMU modules give you the ability to operate as a constant current (CC) or constant voltage (CV) load to create battery charge and discharge profiles. This mode includes static and dynamic operation.

Dynamic current drain solution

The Keysight N6780 Series SMUs visualizes current drain from nA to A in one pass to unlock insights to deliver exceptional battery life. With the ability to accept up to four DC power modules, Keysight’s N6705 power analyzer mainframe provides unrivaled productivity gains in the sourcing and measuring DC voltage and current to and from a DUT. It integrates advanced power supplies with DMM, scope, arb, and data logger features. As a result, the N6705 power analyzer mainframe eliminates the need to use multiple test instruments to create complex test setups, including current probes and shunts, before measuring current into your DUT.

Adding the N6781A or N6785A two-quadrant SMU to the N6705 power analyzer mainframe creates an integrated solution that includes DC sourcing and built-in measurement capabilities that simplify the battery process drain analysis. Key features include seamless measurement ranging, programmable output resistance, and an auxiliary DVM.


A typical wireless device has several subcircuits and uses a power management integrated circuit (PMIC) or power management unit (PMU). Figure 1 is an example of a PMU providing bias voltages independent and regulated to each subcircuit — making it possible to adjust the power to each subcircuit and turn each one on or off, as needed. Channel 1 was the battery emulator, which also measured the total current drain. Channel 2 configuration is “current measure only” mode; this setting records the subcircuit current drain.

Recommended Setup

                                            Measuring subcircuit current drain

Picture 2

 

 

 

 

 

 

 

Figure 1 Use this test configuration to measure current drain from multiple subcircuits within a single DUT

Conclusion
Battery consumption is a critical part of a device’s performance. The measurement ranging feature available Series two-quadrant SMU modules overcome accuracy shortcomings of traditional approaches that use current transducers. This measurement feature dynamically adjusts the measurement range to allow the highest accuracy at each point in the battery run-down current waveform.

The N6781A and N6785A two-quadrant SMUs modules and N6705 power analyzer mainframe will help you evaluate battery run time using advanced power supplies with seamless measurement ranging, programmable output resistance, and an auxiliary DVM.

For more information, please visit: N6700 Series system power supplies

N6781A / N6785A two-quadrant SMU modules : www.keysight.com/sg/en/products/dc-power-supplies