Electronic Design

Battery-Management Chip Is Space- And Cost-Conscious

The DS2438 Smart Battery Monitor stores battery-specific data and tracks battery parameters, including temperature, voltage, current, and remaining charge. It then provides battery data and measurements to the host system's processor, where charge control and remaining-charge algorithms are executed in software. By doing so, it makes battery management cost-effective for portables.

Meanwhile, its 1-Wire network technology lets the pack-resident DS2438 communicate with portable products over a single wire. This network allows products and battery packs to connect through just three electrical contacts—power, ground, and data—minimizing connector cost and maximizing reliability. Each monitor provides its battery pack with a guaranteed-unique 64-bit net address, so multiple battery packs can be wired to one bus but addressed individually. Products then can simultaneously connect to two or more batteries, supporting dual-battery operation or gang charging.

This monitor supplies 40 bytes of nonvolatile EEPROM memory for storage of battery-specific data. Portable products can read this memory over the 1-Wire network to identify the chemistry, capacity, and construction of the battery pack and configure themselves for that particular battery. Since this memory can be rewritten as needed, data that frequently changes also can be stored inside the battery pack. The EEPROM memory maintains stored data even when the battery is completely discharged or momentarily short-circuited.

The DS2438 also includes a complete set of battery instrumentation. It measures battery temperature with 0.03°C resolution and battery voltage with 10-mV resolution. Also, it measures battery current with 10-bit resolution while integrating current over time to facilitate fuel gauging. An offset cancellation feature improves current-measurement accuracy over previous devices. And all of this measurement data is available to the portable product for charge control, remaining-charge estimation, and other battery-monitoring tasks.

In 10,000s, the DS2438 costs $1.15 each. It comes in an 8-pin SOICs.

Dallas Semiconductor, 4401 S. Beltwood Pkwy., Dallas, TX 75244; (972) 371-6085; fax (972) 371-3715; www.dalsemi.com.

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