Dallas - Texas Instruments Inc.'s newest battery management chip set is aimed at two-, three- or four-series cell battery packs used in portable medical appliances, notebook computers, and equipment for test and measurement and industrial applications. The three-chip set consists of the bq2084 smart-battery specification version 1.1-compliant gas gauge IC, the bq29312 analog front-end protection device and the bq29400 secondary-protection IC.
The bq2084 maintains an accurate record of available charge in lithium ion or lithium polymer batteries and is a key piece of the battery management chip set, according to TI. The device monitors capacity and other critical parameters of the battery pack, and reports the information to the system host controller over a system management bus interface. The host controller, such as a DSP, manages remaining battery power to extend system run-time. The bq2084 provides LED display drivers and a pushbutton input to depict remaining battery capacity from full to empty in 20 percent, 25 percent or 33 percent increments with a three-, four- or five-segment display.
Features of the bq2084 include an integrated time base that removes the need for an external crystal. Integrated flash memory eliminates the need for external E2PROM. There is an on-chip, 16-bit delta-sigma converter for accurate voltage and temperature measurements.
The bq29312 provides safety protection for overcharge, overload, short-circuit, overvoltage and undervoltage conditions with the battery management host processor. In overload and short-circuit conditions, the bq29312 turns the FET drive off autonomously. In addition to incorporating a 3.3-volt, 25-milliamp low-dropout regulator, the bq29312 integrates an I2C-compatible interface to enable measurement of battery parameters such as cell voltages and pack temperature. Current protection thresholds and delays, cell balancing drive, power modes and feature configurations can be programmed into the bq29312 to increase the flexibility of the battery management system.
Overvoltage detector built in
The bq29400 secondary-protection IC incorporates a highly accurate independent precision overvoltage detection circuit. With the secondary-voltage protector, each battery cell in a multicell battery pack is compared with an internal reference voltage. If one cell gets into an overvoltage condition, the bq29400 will wait over a programmed period of time and set an output to drive an external FET, which can be used to burn a chemical fuse to further protect the system. The device's power consumption is less than 2 microamps, according to TI.
All three components of the chip set are available now from TI and its authorized distributors. The bq2084 comes in a 38-pin thin-shrink small-outline package, the bq29312 in a 24-pin TSSOP and the bq29400 comes in an eight-pin TSSOP. Suggested resale pricing in 1,000-piece quantities is $4.35 each for the bq2084, $1.20 each for the bq29312 and 45 cents each for the bq29400. A combined evaluation module is available for all three devices.
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