Stand-Alone Battery Fuel Gauge Calculates Remaining Battery Capacity and Reduces Software Development Efforts for 1- and 2-Cell Applications
DALLAS, TX-January 20, 2006-Dallas Semiconductor (NASDAQ: MXIM) introduces the DS2781 stand-alone fuel gauge. Operating directly from a 2.5V to 10V power source, the DS2781 calculates remaining capacity for 1- or 2-cell Li+ and Li+ polymer battery packs. The device includes 16-bit current measurement, and 11-bit voltage and temperature measurements. On-chip nonvolatile memory stores cell characterization data and application performance parameters. The DS2781 uses this measured and stored data to calculate the remaining battery capacity. Additionally, the on-chip algorithms and status reporting capabilities reduce the amount of interaction necessary between the device and the host processor. Software development is thus greatly simplified.
The DS2781 measures current by calculating the voltage drop across a low-value sense resistor. Programming can compensate the current-sense resistor to correct for variation in its value over temperature, thus allowing use of lower cost sense resistors without compromising current measurement accuracy. To improve current measurement accuracy even further, the DS2781 also provides automatic current-offset correction and user-programmable gain compensation.
Additionally, the DS2781 contains 40 bytes of EEPROM: 24 bytes to store the cell characterization data and application parameters, and 16 bytes for use by the host system or pack manufacturer. Communication between the device and the host is handled through a 1-Wire(R) interface, reducing the number of pack contacts to a single wire.
Typical applications for the DS2781 include digital video cameras, commercial two-way radios, industrial PDAs, handheld PC data terminals, and portable GPS navigation systems. The device is available in a tiny lead-free 8-pin TSSOP package, small enough to fit on the side of a prismatic battery cell. Prices start at $2.90 (1000-up, FOB USA).
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