DALLAS Semiconductor, represented in Australia by Arrow Electronics , has released the DS2780 standalone fuel gauge. It calculates remaining capacity for Li-Ion and Li-Ion polymer batteries without the need for host-side fuel-gauging algorithms. This allows it to greatly simplifies software development.
The device provides 16-bit current measurement, 11-bit voltage and temperature measurement, and on-chip nonvolatile memory to store cell characterisation data and application performance parameters. It uses this data to calculate the remaining capacity. On-chip algorithms and status-reporting capabilities automatically send alerts to the host processor. This reduces 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. The DS2780 also includes automatic current-offset correction and user-programmable gain compensation, improving current-measurement accuracy.
It contains 40 bytes of EEPROM, 24 bytes are used to store the cell-characterisation data and application parameters and 16 bytes are used by the host system or pack manufacturer. Communication between the device and the host is handled through a one-wire interface, which minimises the number of pack contacts.
Typical applications include digital still cameras, subnotebook computers, handheld PC-data terminals, and 3G multimedia wireless handsets. The device is available in an eight-pin TSSOP package, small enough to fit on the side of a prismatic battery cell.