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Li-ion safety monitor controls six voltages, two temp inputs

Posted: 18 Mar 2010 ?? ?Print Version ?Bookmark and Share

Keywords:Li-ion battery? battery monitor? signal isolator?

AD8280 safety monitor

Analog Devices Inc. has launched a Li-ion battery monitoring and protection system that integrates all necessary components, including voltage and current measurement, signal isolation and safety monitoring.

Compared to NiMH batteries, Li-ion batteries have a better energy-to-weight ratio, offer more efficient storage capacity over multiple charge-discharge cycles, and suffer less charge leakage when not in use. And unlike NiMH batteries traditionally used in high-voltage applications, battery stacks using Li-ion technology can comprise a large number of individual cells totaling hundreds of volts. Each cell must be properly monitored and balanced to ensure user safety, improve battery performance and extend battery life. ADI's new Li-ion battery monitoring and protection system performs these functions while also allowing power system designers to replace costly discrete components, decrease power consumption and reduce system space.

"Li-ion batteries must be treated with respect. Fires have occurred in notebook computer applications because over-voltage peaks were not monitored correctly," said Steve Sockolov, director, Precision Signal Processing group, Analog Devices. "Although the quality of battery fabrication has improved, guarding against higher temperature conditions in any energy, industrial or automotive application is critical."

ADI offers the main components required for a complete Li-ion battery monitoring and protection system. The voltage measurement device monitors and balances the cells (AD7280), while the current measurement device monitors the cell stack's current (ADuC703x or AD821x). The isolator brings the measurement signals across the high-voltage barrier to the battery management unit (ADuM140x or ADuM540x), the safety monitor enables creation of a fail-safe circuit and safe environment to the user (AD8280) and the battery management unit controls and manages battery functions to optimize operation (Blackfin ADSP-50x).

The Li-ion battery monitoring and protection system includes a safety monitor, the AD8280. The new safety monitor provides the designer with the final piece needed to develop the complete front-end of a battery monitoring and protection system. The AD8280 is an integrated solution that monitors six cell voltages and two temperature inputs. It is powered completely from the battery stack providing either a shared or a separate alarm for any of three conditionsover-voltage, over-temperature or under-voltage.

Other benefits include extensive self-test upon prompt enhancing the designers ability to meet functional safety requirements such as ISO26262 and IEC61508. The device also offers large, continuous range-of-trip point settings that provide the flexibility to work with any Li-ion battery chemistry. In addition, the solution offers flexible safety monitor configurations as well as communications daisy-chain option that minimizes the need for isolators in a high-voltage cell stack.

Low-power mode enables the user to minimize battery drain when the battery is not in use. The device is also compliant with AEC-Q100 and EMI (electromagnetic interference) standards, making the part suitable for automotive applications.

The AD8280 Li-ion battery safety monitor is sampling now at $3.49 per unit in 1,000-unit shipments in a 48-lead LQFP (low-profile quad package).

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