Stand-Alone Fuel Gauge Calculates Remaining Battery Capacity and Simplifies Software Development
DALLAS, TX—December 21, 2004—Dallas Semiconductor (NASDAQ: MXIM) introduces the DS2780 stand-alone fuel gauge. The DS2780 calculates remaining capacity for Li-Ion and Li-Ion polymer batteries without need for host-side fuel-gauging algorithms. Thus, the DS2780 greatly simplifies software development.
The device provides 16-bit current measurement, 11-bit voltage and temperature measurements, and on-chip nonvolatile memory to store cell characterization data and application performance parameters. The DS2780 uses this measured and stored data to calculate the remaining capacity. Additionally, the DS2780's on-chip algorithms and status-reporting capabilities automatically send alerts to the host processor. This reduces the DS2780's amount of interaction with the processor and frees the processor for other operations.
Current is measured in the DS2780 by calculating the voltage drop across a low-value sense resistor. The device can be programmed to compensate the current-sense resistor to correct for variation in its value over temperature. This allows the use of lower cost sense resistors without compromising current measurement accuracy. To improve current-measurement accuracy even further, the DS2780 also includes automatic current-offset correction and user-programmable gain compensation.
Additionally, the DS2780 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® interface, which minimizes the number of pack contacts.
Typical applications for the DS2780 include digital still cameras, subnotebook computers, handheld PC-data terminals, and 3G multimedia wireless handsets. The device is available in a tiny 8-pin TSSOP package, small enough to fit on the side of a prismatic battery cell. Prices start at $2.60 (1000-up, FOB USA).
1-Wire is a registered trademark of Dallas Semiconductor Corp.
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