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Battery fuel gauge does measurement, data storage

Posted: 05 Jun 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Dallas Semi? DS2756? gauge? battery fuel?

Dallas Semiconductor has introduced the DS2756, a battery fuel gauge that integrates current, voltage, and temperature measurements along with nonvolatile data storage into one IC. This device contains three power statesactive, sleep and a unique 'suspend' modes. Suspend mode allows the device to optimize its own current drain while other devices in the host enter low-power inactive states. Suspend mode thus extends the battery and operational life of the host product, explained Dallas Semi.

The new device periodically cycles between suspend mode and active mode to measure current at a reduced supply as low as 10A, said the company. Cycling between these power states lets the device detect if the pack is being discharged or charged above programmable low-current suspend thresholds. If it detects either of these conditions, it sends a microcontroller or other pack circuitry a wake-up alert to begin normal active operation.

The device measures current, average current and accumulated current. Using a 20mW sense resistor, current accumulation is performed over a range of 3.2A. An external filtering capacitor allows peak currents of higher values to be integrated in the current-accumulation (fuel-gauging) measurement. Accumulated current is reported with an accuracy of 2 percent of reading, 3.9V over a range of 64mV. Standby currents are measured with an accuracy of 195#956;A, added the company.

Voltage is measured up to 4.75V with a resolution of 4.88mV. Temperature is measured over the entire operating range with a resolution of 0.125C, said Dallas Semi. If either the accumulated current or the temperature measurement exceeds user-programmed limits, the device sends an interrupt to the host processor to indicate that the event has occurred. A unique 'snapshot' mode allows both current and voltage measurements to be synchronized, so the device can obtain an instantaneous power measurement for a specific single event, said the company. All measured data is stored in on-chip EEPROM or SRAM memory, and can reported to the host through the device's 1-Wire communication interface.

Typical applications for the device include handheld wireless products such as multimedia players, mobile phones, PDAs and digital cameras. The device is available in an 8-pin TSSOP package, small enough to easily fit on the side of a Li+ prismatic cell and thus ideal for battery packs, said Dallas Semi.

Prices start at $1.90 (1,000-up, FOB USA).

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