Maxim Unveils Small, Stand-Alone, Multicell Li+ Battery Fuel Gauge To Integrate LED Drivers & A Pushbutton Input
Maxim Integrated Products introduced the DS2788, described as the industry’s smallest stand-alone fuel gauge to integrate LED drivers and a pushbutton input for multiple Li+ cells into a single IC. Designed for the tight space of a battery pack, it is packaged in a lead-free 14-pin TSSOP. The DS2788 is suitable for displaying the remaining battery capacity of power tools, ebikes, portable household appliances, and ultra-mobile PCs.
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, thus reducing board space and system cost. A programmable I/O pin that can be configured as a debounced-pushbutton input enables the LED display.
To reduce the need for software development and shorten time-to-market, the DS2788 utilizes 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. The fuel gauge accurately monitors battery packs with multiple Li+ cells by allowing internal gain calibration of an external voltage-divider that feeds the battery-voltage-measurement input. To conserve battery power, a pin for driving external FET switches enables the voltage-divider only during voltage measurement. An estimate of the battery pack’s capacity is communicated to the host over a 1-Wire® interface, which reduces the number of necessary contacts between the pack and the host to as few as three.
Additionally, the DS2788 provides 16 bytes of EEPROM for the exclusive use of the host system and/or pack manufacturer. This EEPROM can be used to facilitate 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 assures that no two DS2788s are alike and enables absolute battery-pack traceability.
Prices start at $2.72 (1000-up, FOB USA).
