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Battery charge controller integrates SMBus interface

Posted: 28 Dec 2005 ?? ?Print Version ?Bookmark and Share

Keywords:Texas Instruments? TI? System Management Bus? SMBus? bq24721?

Battery charge controller with SMBus interface

Texas Instruments Inc. unveiled its first integrated battery charge controller with a System Management Bus (SMBus) interface aimed at multi-cell, multi-chemistry battery packs used in portable applications.

The new bq24721 charge management device interfaces to a system's host controller through an SMBus communications interface. The charger offers 0.4 percent accuracy on charge voltage regulation and two percent accuracy on current amplifier outputs. Using a synchronous NMOS-NMOS rectifier, this product can achieve power efficiencies of up to 94 percent.

The bq24721 integrates several features, including the system power selector function, which automatically selects the AC adaptor or the battery to properly manage the system load. The device's dynamic power management function controls the charge current depending on system load conditions, avoiding AC adaptor overload. In addition, current sense amplifiers enable measurement of either the charge current or the AC adaptor current, allowing termination of the "non-smart" packs and monitoring of overall system power.

Key features of the bq24721 chip include:

  • NMOS-NMOS synchronous DC/DC buck converter with user-selectable 300kHz or 500kHz frequency;
  • Programmable battery voltage, charge current and AC adaptor current via SMBus;
  • Charge management: 0.4 percent charge voltage accuracy, 3 percent charge current regulation accuracy and 3 percent adaptor current regulation accuracy;
  • Two percent accuracy integrated charge and AC adaptor 20x current amplifier output;
  • Autonomous power source selector and dynamic power management;
  • Battery pack voltage range 0 to 19.2V for three- to four-cell Li-ion series cells;
  • AC adaptor operating range 8V to 28V; and
  • Charger soft start, charge over-current protection and IC temperature monitoring.

The bq24721 battery charge management IC comes in a 32-pin, 5-by-5mm QFN package, with a suggested retail pricing of $4.90 in 1,000-piece quantities.

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