Cell-Phone Battery Drain Analysis Using LXI
It has happened to all of us. You pick up your cell phone to answer an important call, and the message on the screen displays low battery. “Why now?” we ask ourselves, “I just charged my cell phone!”
Today, mobile devices such as smartphones, and the seemingly countless number of applications available on them, are an integral part of everyday life. However, the power-intensive applications that we can’t seem to live without, along with the usage of external communications such as Wi-Fi and Bluetooth, quickly take a toll on the battery life of the device.
| Figure 1. Battery Current Drain Analysis Test Solution |
Fortunately, new test instruments are designed specifically for battery current drain analysis, enabling product designers more accuracy when predicting battery life vs. real-world usage. One such example is the Agilent Technologies battery current drain analysis test solution that contains three main elements: the N6705B DC power analyzer, the N6781A two-quadrant source/measure unit (SMU), and the 14585A control and analysis software (Figure 1).
The N6705B DC power analyzer is a LAN eXtensions for Instrumentation (LXI) instrument enabling high-speed communications of measurement data over Ethernet to the PC and ensuring consistent interoperability and synchronization with other LXI-compliant instruments.
Figure 2 illustrates Agilent’s integrated source/measurement solution for battery current drain analysis. The N6781A SMU measures data as the DUT transitions between different operating states, creating a dynamic current consumption that ranges from submicroamperes to amperes. Measuring these 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 not possible with typical instruments such as DMMs, oscilloscopes, current probes, conventional SMUs, or multiple shunt resistors.
| Figure 2. Integrated SMU Solution for Battery Current Drain Analysis |
In addition, by communicating to the PC via LAN utilizing the LXI standard, the test solution is ideally suited for distributed applications or remote testing and diagnostics where the DUT and PC are not co-located and often span different regions or countries. LXI provides the power and flexibility that other PC interconnectivity solutions such as USB or GPIB cannot.
The N6781A can be configured to test various applications such as battery discharge operation, battery-charger circuit testing, and battery run-down testing. Figure 3 shows an example of battery run-down test.
| Figure 3. Battery Run-Down Test Setup |
Using a real battery will help reveal how a device behaves as a system and determine if it operates as expected in terms of low-voltage conditions, battery life, and more. In Figure 3, a battery powers the DUT, and the N6781A is connected in series to make the current drain measurement. By automatically regulating a zero-volt drop across the module, this mode turns the N6781A into a zero-burden ammeter and eliminates the problems that typically occur with shunt resistors in traditional setups. The N6781A also offers an auxiliary DVM that can be connected across the battery to analyze voltage run-down and determine watt-hours of energy used.
Taking advantage of the N6705B’s LXI capabilities allows you to transfer acquired data from the battery-drain analysis test solution over high-speed Ethernet to the PC for further analysis using Agilent’s 14585A control and analysis software. As shown in the trace in Figure 4, you can place markers on the current drain profile to help achieve useful insights into DUT behavior.
| Figure 4. Trace of Battery Drain Analysis Testing |
Mobile devices are an integral part of everyday life. We rely upon them and the energy-consuming graphic-intensive applications to simplify our daily tasks and entertain us. While there are many steps that you can take to make a cell phone battery last longer, the battery eventually will need to be recharged.
Thankfully, today’s advanced testing solutions for battery current drain analysis enable product designers to provide better estimates of battery life for real-world usage and set realistic expectations for users. Test solutions based upon the LXI standard offer a level of convenience that is well suited to the distributed nature of companies today whose workforce often is disbursed geographically over a wide area either domestically or internationally.
About the Author
Ed Brorein is a marketing applications engineer at Agilent Technologies. He joined the company (then Hewlett-Packard) in 1979 and has worked as an R&D engineer, manufacturing engineer, and marketing engineer. Brorein received a B.S.E.E. from Villanova University in 1979 and an M.S.E.E. from the New Jersey Institute of Technology in 1987.