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Li-ion battery fuel gauge IC

Chip integrates LED display drivers and a pushbutton input

Maxim designed the DS2788 for applications such as power tools, electric bicycles, portable household appliances, or ultra-mobile PCs, that benefit from an LED display that shows the remaining battery capacity. It integrates multiple dedicated LED drivers and a pushbutton input in a 14-pin TSSOP package. The DS2788 reports a battery pack's remaining capacity in both "mAh remaining" and "percentage of full" to the host system, and it displays the results using either four or all five of its integrated LED driver outputs. Capable of directly sinking current, each LED driver pin requires only a single resistor to set its current in the LED display. A programmable I/O pin that can be configured as a debounced-pushbutton input enables the LED display. The chip uses an embedded fuel gauge algorithm to calculate remaining capacity based on precision coulomb count, discharge rate, temperature, and cell characteristics, along with precision battery-current and voltage measurements. It monitors battery packs with multiple Li+ cells by allowing internal gain calibration of an external voltage-divider that feeds the battery-voltage-measurement input. 16 bytes of EEPROM is available to the host system and/or pack manufacturer, for battery-lot and date tracking, as well as for the nonvolatile storage of system or battery-usage statistics. A unique, factory-programmed 64-bit ROM ID enables absolute battery-pack traceability. The chip costs from $2.72 (1000).