Chip Monitors Safety of Lithium-Ion Battery Stacks

A new safety monitoring chip from ADI enables tier-oneautomotive suppliers to design monitoring and protection systems for themassive lithium-ion battery packs used in electric cars and plug-in hybridvehicles.

The newchip can monitor six cells at a time, and can be daisy-chained with other chipsto look for over-voltage, over-temperature or under-voltage conditions inbattery packs composed of hundreds or even thousands of cells.

"It givesthe car manufacturers peace of mind," says Steve Boyle, product marketingmanager for Analog Devices Inc. "Itprovides assurance that they can design a system that's safe." Boyle says thetechnology could also be used for high-voltage industrial, automotive andenergy applications, such as wind turbines and photovoltaic cells.

Known asthe AD8280,the new safety monitoring chip is particularly significant for safety-relatedapplications, where high temperatures or voltages can damage batteries, orworse, cause unsafe conditions. It's made up of a series of high-voltagecomparators that "look" for undesirable voltage or temperature conditions andthen work with an alarm to let the system know if any values have gone outsidea prescribed window of acceptability.

AnalogDevices engineers say that one of the big advantages of the device is that itcan be easily daisy-chained to work with large battery stacks. Because it's anintegrated package and not a conglomeration of discrete electronic components,daisy-chaining of the AD8280 can also take place without a need for isolatorsat each stage.

The safetymonitoring chip is incorporated in a 48-lead, low-profile quad flat package(LQFP) that measures just 7 x 7 mm square.

"You couldbuild this up discretely, but the discrete systems take up more space and costa lot," says Sam Weinstein, a product manager for the AD8280. "We've been ableto integrate all these functions into one chip."