Protection and safety monitor
23 March 2010
ADI’s high-performance signal processing technology simplifies Li-ion battery protection.
Lithium-ion (Li-ion) batteries are growing in popularity as energy storage reservoirs for high-voltage energy, industrial and automotive applications, such as wind turbines, photo-voltaic cells, and hybrid electric vehicles, and this has spurred demand for safer, higher performing battery monitoring and protection systems.
Analog Devices has addressed the requirements of Li-ion battery manufacturers and power system designers with the unveiling of 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 (nickel-metal hydride) 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 totalling 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 of Precision Signal Processing Group at 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, including:
• Voltage measurement device - monitors and balances the cells (AD7280)
• Current measurement device - monitors the cell stack’s current (ADuC703x or AD821x)
• Isolator - brings the measurement signals across the high-voltage barrier to the battery management unit (ADuM140x or ADuM540x)
• Safety monitor - enables creation of a fail-safe circuit and safe environment to the user (AD8280)
• Battery management unit – controls and manages battery functions to optimise operation (Blackfin ADSP-50x )
The AD8280, Li-ion battery monitoring and protection system includes a safety monitor, which 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 conditions; over-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
• Large, continuous range-of-trip point settings provide the flexibility to work with any Li-ion battery chemistry
• Flexible safety monitor configurations
• Communications daisy-chain option minimises the need for isolators in a high-voltage cell stack
• Low-power mode enables the user to minimise battery drain when the battery is not in use
• 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 in a 48-lead LQFP (low-profile quad package).
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