Tiny Battery Gauges Include Li+ Protector

A family of two-cell, stand-alone battery fuel gauges are the first to integrate a two-cell lithium-ion (Li+) protector in a 3- by 5-mm TDFN package. The DS2775, DS2776, DS2777, and DS2778 estimate available capacity based on coulomb count, discharge rate, temperature, and cell characteristics. Additionally, the DS2776 and DS2778 integrate SHA-1 authentication for battery security. To reduce development effort and time-to-market, the gauges combine a precision, analog front-end for measuring current and voltage with a proprietary, embedded FuelPack fuel-gauge algorithm. On-chip temperature measurements eliminate the need for a thermistor in the battery pack. The devices also can use temperature data to enable gain and temperature-coefficient compensation in the current measurement, which allows the use of a low-cost current-sense resistor. In addition to nonvolatile storage for cell compensation, application parameters, cycle counter, and age estimation, the DS2775-DS2778 integrate 16 bytes of EEPROM memory to facilitate battery lot and date tracking or nonvolatile storage of system and battery-usage statistics. The gauges enable battery packs to meet IEEE 1625-2008 safety, identification, and authentication requirements. Prices start at $2.94 in quantities of 1000. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.