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Battery fuel gauge targets wireless apps

Posted: 06 Jun 2006     Print Version  Bookmark and Share

Keywords:Dallas Semi  DS2756  gauge  battery fuel  nonvolatile data storage 

Dallas Semiconductor has introduced a battery fuel gauge called the DS2756. This device integrates current, voltage, and temperature measurements along with nonvolatile data storage into one IC. This device contains three power states—active, sleep and a unique 'suspend' modes. Suspend mode allows the device to optimise 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 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 ±two per cent of reading, ±3.9μV over a range of ±64mV. Standby currents are measured with an accuracy of ±195#956;A, added the company.

This device periodically cycles between suspend mode and active mode to measure current at a reduced supply as low as 10μA, 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.

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 0.125°C, 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 Rs.85.71 ($1.90) (1,000-up, FOB USA).

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