Dallas Semiconductor DS2786: Stand-alone fuel gauge reports battery capacity without a full-charge cycle
Using a combination of an OCV (open-circuit-voltage) battery model and coulomb counting, the stand-alone DS2786 OCV-based fuel gauge estimates the available capacity of rechargeable lithium-ion batteries. The device provides accurate capacity information immediately after a user connects a battery pack to the host. During moderate- to high-discharge rates, the fuel gauge uses coulomb counting as a secondary method of estimating relative capacity. Able to detect pack capacity from a partial charge or discharge cycle, this feature eliminates the need for a full charge or discharge cycle. Features include a 12-bit voltage measurement with ±10-mV accuracy and 1.22-mV resolution; a bidirectionally measured current with 11-bit resolution; and two auxiliary voltage inputs aiming at measuring resistor ratios, suiting thermistor or pack-identification-resistor measurement. Additional features include an I2C interface, and an OCV-look-up table and other parameters stored in 32 bytes of on-chip EEPROM. Internal measurements provide ±3°C accuracy. Measuring 3×3 mm in a TDFN-10 package, the DS2786 costs $1.22 (10,000).
Dallas Semiconductor, www.dallassemi.com
