Battery management ICs protect lithium battery packs

Texas Instruments Inc. has launched three new smart battery management ICs that improve measurement and protection of multicell, lithium-based battery packs. The controllers simplify design in multicell lithium-based rechargeable batteries used in uninterruptible power supplies and applications, such as cordless power tools, power-assisted bicycles, and portable medical and test equipment.

TI's bq78PL114 battery management controller provides complete lithium battery system control, monitoring and safety functions for 4-series cells. The device integrates accurate battery fuel gauge technology with extremely efficient cell balancing, short-circuit detection and battery protection. The bq78PL114 is completely user-configurable with parametric tables set in flash memory to support a variety of Li-ion and Li-polymer chemistries, operating conditions, safety control and data reporting design requirements. The device can be configured easily using TI's bqWizard fully programmable GUI and requires no algorithm or firmware development.

In addition to the controller, TI also introduced its bq76PL102 dual-cell battery monitor, which performs simultaneous voltage and temperature monitoring of each cell and reports those parameters over TI's PowerLAN communications interface. By leveraging the PowerLAN interface, a designer can combine multiple bq76PL102 monitor devices with the bq78PL114 controller to create a smart battery solution for up to 12 rechargeable cells. Real-time communications is possible in all operating conditions, even during widely fluctuating load conditions. The scalable PowerLAN architecture also provides robust communications in tough electromagnetic and radio frequency interference situations, while avoiding excess power draw and a large number of discrete components.

Precise cell balancing
Partitioning of the battery monitoring function cell-by-cell enables a more accurate state of charge measurement. With this in mind, the bq78PL114-based system helps extend battery life and system runtime with TI's patented PowerPump cell balancing technology. This technology uses a charge-transfer methodology that does not waste excess energy as heat, but moves energy dynamically from cell to cell with very high efficiency. Precise balancing occurs at every stage of operation—at charge, discharge and rest. With PowerPump technology, cell balancing is automatically coordinated between all cells in the system.

TI also added another degree of integration, safety and protection to multi-cell applications with a new lithium-based battery protector and analog front end for 5- to 10-cell battery systems. The bq77PL900, which includes an I?C interface for communication with a host controller, can also operate as a stand-alone battery protection circuit. The device integrates a 5V and a 3.3V LDO to help power the host controller or other circuits in the system.

The low-power battery protection circuit includes a voltage translation system to measure temperature, system current and individual cell voltages. Cell balancing can be performed through bypassing current around selected cells. The bq77PL900 also provides full safety protection for overvoltage, undervoltage, overtemperature and overcurrent in discharge and short circuit during discharge conditions.

The bq78PL114 battery management controller and the bqPL900 lithium-based battery protector are available in volume. The bq78PL114 comes in a 48-pin, 7mm x 7mm QFN package, with a suggested resale price of $5.65 in 100-piece quantities. The bq77PL900 comes in a 48-pin SSOP package, and has a suggested resale price of $3.70 in 100-piece quantities. The bq76PL102 is currently sampling with expected availability later in Q4 08. It comes in a 16-pin, 3mm x 3mm QFN package, with a suggested resale price of $1.90 in 100-unit quantities.