Simple micropower fuel gauge reduces quiescent current and size

Paul Boughton

Maxim Integrated Products has developed a simple low-power fuel gauge for Lithium-ion (Li+) batteries that dramatically reduces the power consumption and space required in portable designs.

Operating at only 23µA, this battery fuel gauge uses four times less power than competitive devices and even less in micropower hibernate mode, in which the fuel gauge continues to operate. It needs only one external capacitor, not multiple external devices, so it simplifies the design and shrinks the space required by a factor of three. The gauge is ideal for portable battery-powered applications where size, cost, and power are critical, such as smartphones, wireless handsets, and mobile accessories, including Bluetooth headsets, portable speakers, fitness devices, and Wi-Fi routers.

“Although fuel gauges have traditionally been found in notebook computer applications, they are increasingly appearing as a critical ‘must-have’ element in consumer devices. With a highly accurate fuel gauge, customers know how much battery is left in their mobile device and that gives them confidence in the product,” said Susie Inouye, Principal Analyst of Databeans.[Page Break]

Traditional fuel gauge designs require multiple external components including current-sense resistors, which increase both bill of materials (BOM) cost and design complexity. Those fuel gauges also use coulomb counting, which can drift and affect the accuracy of the gauge over time.

The MAX17048 features the proven ModelGauge algorithm and does not require coulomb counting to report accurate battery state-of-charge, thus extending runtime. [Page Break]

The MAX17048 functionality is also integrated into the company’s TINI Power System-on-Chip (SoC) to make it easier to upgrade designs to more complex systems.

The ModelGauge algorithm provides accurate state of charge and compensates for temperature and load variation and also eliminates the need for the current-sense resistor required in competing coulomb-counting fuel gauges. The gauge automatically detects when the battery enters a low-current state and switches into a low-power 4µA hibernate mode, while still providing accurate fuel gauging. the chip automatically exits hibernate mode when the system returns to active state.

“Mobile device manufacturers are increasingly paying attention to enhancing user experience to set themselves apart from their competition,” said Bakul Damle, Business Director at Maxim Integrated. “Having a simple but trustworthy fuel gauge to correctly inform the user about the battery status as well as improve runtime goes a long way in achieving this goal.”

The MAX17048 is available in an 8-bump WLP package (0.9mm x 1.7mm) and an 8-pin TDFN package (2mm x 2mm) from $1.12.

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