Single-Cell, Stand-Alone Fuel Gauge Claims Industry First

Hailed as an industry first, the DS2784 1-cell, stand-alone fuel gauge integrates a 1-cell Li+ protector and SHA-1 authentication in a 3 mm x 5 mm TDFN package. Reportedly, three separate ICs have been required to give the same functionality that the DS2784 provides. Small enough to fit on the side of a prismatic battery cell, the DS2784 targets space-sensitive portable applications that use 1-cell Li+ battery packs. The fuel gauge estimates available capacity based on coulomb count, discharge rate, temperature, and cell characteristics. It also combines a precision, analog front-end for measuring current and voltage with a proven, embedded fuel-gauge algorithm. On-chip temperature measurements eliminate the need for a thermistor in the battery pack. Additionally, the DS2784 can use temperature data to enable gain and temperature-coefficient compensation in the current measurement, thereby allowing the use of a low-cost current-sense resistor. The 1-cell Li+ protector monitors for cell overvoltage, undervoltage, overcurrent, and short-circuit conditions. Thresholds are user-programmable and can be locked to prevent accidental overwrites. A built-in charge pump enables cell protection to be implemented with high-side n-channel FETs. The integrated, secure challenge-response authentication algorithm provides protection against the counterfeiting of battery packs. It utilizes a SHA-1 algorithm with a 64-bit secret and communicates with the host over the DS2784's 1-Wire interface. Prices start at $2.94 each/1000+. MAXIM INTEGRATED PRODUCTS, Sunnyvale, CA. (800) 998-8800.