« Previously: A battery fuel gauge for wearables  

The EZ algorithm is built into the MAX17055 stand-alone single cell pack, fuel gauge IC. With 0.7µA shutdown current, 7µA hibernate current and 18µA active supply current, the device is ideal for battery-operated wearable devices. The I2C interface provides access to data and control registers.

System error competitive analysis

Figure 2 shows a system error competitive analysis. This histogram illustrates that near empty, the MAX17055 delivers no more than 1% error in most test cases (15 out of 26), while the competitive device exhibits much higher error for the same set of tests.

 
201704_EZSystemError_CompetitiveAnalysis_FuelGauge_Maxim_Figure2_cr Figure 2: System error competitive analysis.  

Low error near empty assures optimum utilisation of the battery charge, maximizing run-time and minimizing unexpected or premature interruption of the device operation.

Using a fuel gauge IC with a low quiescent current extends run-time. The MAX17055’s 18µA quiescent current is 64% lower than that of the nearest competitive device. Further, in low power hibernate mode the device absorbs only 7µA. Applying it to the scenario discussed earlier, the run-time is reduced from 52 minutes down to 7 minutes—a substantial gain in performance.

Conclusion

We have highlighted the critical importance of battery modeling in an effective fuel gauge system to maximize battery run-time accuracy and duration. We discussed the barriers to obtaining accurate battery models, which lengthen time-to-market and impede the proliferation of lower volume battery applications. A disruptive approach, based on the ModelGauge m5 EZ algorithm, embedded in MAX17055, makes battery system development faster, easier, more cost effective, and delivers better battery performance for a broad range of applications.

Nazzareno (Reno) Rossetti is a seasoned Analog and Power Management professional, a published author, and holds several patents in this field. He holds a doctorate in Electrical Engineering from Politecnico di Torino, Italy. Bakul Damle is the Mobile Power Business Management Director at Maxim Integrated at Maxim Integrated. His current interests include battery and power management specifically in fuel gauges, battery charging, energy harvesting, wireless charging, and battery authentication. He has several patents in test and measurement. Bakul holds a Master of Science degree in Electrical Engineering from the California Institute of Technology and a Bachelor of Technology in Engineering Physics from the Indian Institute of Technology.