NEW BATTERY MONITOR FROM DALLAS SEMICONDUCTOR FIRST HIGH-PERFORMANCE FUEL GAUGE TO INTEGRATE Li-ION PROTECTION CIRCUIT AND CURRENT-SENSE RESISTOR
DALLAS, TX-September 25, 2000-Dallas Semiconductor today announced the DS2760 High-Precision Li-Ion Battery Monitor, the industry's first high-performance fuel gauge IC to incorporate a lithium-ion (Li-Ion) protection circuit and an internal 25 mOhm current sense resistor in a 3.25 mm x 2.74 mm, die-sized package. The DS2760's high level of integration translates to significant cost and space savings, making highly sophisticated fuel gauging cost-effective in mainstream portable products.
Widely used in portable communications and handheld instruments, lithium-ion and lithium polymer are among the fastest growing battery chemistries. Lithium's advantages are high energy density with respect to weight and volume, low self-discharge and an operating voltage that allows equipment to be powered by a single battery cell. A lithium-ion protection circuit must continuously monitor the cell for over- and under-voltage, over-current, and short-circuits, terminating charge and/or discharge when a violation is detected. The DS2760 is the first lithium-ion monitor to integrate this required feature with precision fuel gauge capability, removing a major cost consideration from lithium-ion technology.
A low impedance sense resistor is a required component for fuel gauging. A sense resistor is a costly precision component that consumes precious board space in ever-shrinking battery packs. Deposited in the DS2760 flip chip fabrication process, the sense resistor consumes no PCB area and incurs no additional cost in the battery pack.
Mike Overlaur, Dallas Semiconductor's battery management marketing manager, said, "The DS2760 is a monolithic data acquisition, information storage, and lithium-ion protection device, tailored for cost-sensitive battery pack applications that demand high performance. The inclusion of the protector and the sense resistor in the same chip as the fuel gauge IC marks a significant advancement in space and cost-sensitive intelligent battery packs."
The DS2760's integrated data acquisition features include a signed12-bit current ADC, a 10-bit voltage ADC, and a signed 10-bit temperature sensor, all of which eliminate pack-resident data converters and thermistors. The DS2760 accumulates current measurements over time to facilitate the estimate of remaining battery capacity, called fuel gauging. Besides saving space and cost, sense resistor integration also enhances fuel gauge precision. With the sense resistor built onto the die, process variations can be trimmed out during manufacture of each individual DS2760. Furthermore, the DS2760 automatically and continuously performs offset corrections of the current A/D converter in real time, providing for an accurate fuel gauge without burdening the host system with time-consuming calibrations. The DS2760 also uses the on-chip thermal sensor to continuously and automatically compensate for the temperature coefficient of the integrated sense resistor, again enhancing fuel gauging precision.
The DS2760 includes 32 bytes of user-lockable EEPROM for true nonvolatile storage of critical data such as chemistry, cell capacity, date of manufacture, warranty, and cycle count. EEPROM prevents loss of this critical data in the event of battery contact shorts or ESD. An additional 16 bytes of SRAM are available for storing non-critical dynamic information.
The DS2760 communicates with the host processor over a multi-node 1-Wire® digital interface. The 1.8V logic-level 1-Wire interface digitally transfers data between the battery pack and host over a single wire, minimizing noise susceptibility, battery contacts and overall pack cost. Each DS2760 also has a unique network address that inherently supports multi-battery operation.
Overlaur said, "The manufacturer of DS2760-based products also gains an innovative capability unique to the DS2760. The empowered host can override the on-state of the protection FETs, disabling charging and/or discharging under software control. That means firmware can control the power state of the portable product or automatically switch among packs in multi-pack applications using the protection FETs that are already present."
Applications for the DS2760 are in lithium-powered instruments, which include cellular phones, PDAs, digital cameras, camcorders, MP3 players, small handheld data collection equipment, and wireless control devices.
Available in flip-chip and 16-pin TSSOP packages, the DS2760 High Precision Li-Ion Battery Monitor is in production now. The flip chip package is priced at $1.10 in OEM quantities of 1 million.
Dallas Semiconductor manufactures specialty semiconductors focused in three areas: Communications, 1-Wire® and Network Computing, and Mixed Signal. The Company combines proprietary fab and circuit technologies to create innovative products that are sold to over 15,000 customers worldwide. Applications include battery management, broadband telecommunications, wireless handsets, cellular base stations, secure Internet communications, networking, servers, data storage and a wide variety of industrial equipment.
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