A new monolithic flyback DC/DC converter designed to actively balance high voltage stacks of batteries has been released by Linear Technology Corporation. The 
company advises that, battery stacks are commonly found in electric and hybrid vehicles as well as fail-safe power supplies and energy storage systems. It confirms that, because these batteries are stacked in series, the lowest capacity battery will limit the entire battery stack’s run-time. It points out that, ideally, the batteries would be perfectly matched, but this is often not the case and generally gets worse as the batteries age. In address the company adds out that, passive energy balancing offers no improved run-time as it dissipates the added energy of the higher capacity batteries to match the lowest one. In response the company conversely identifies that, its LT8584 offers high efficiency active balancing, which redistributes the charge from the stronger cells (higher voltage) to charge the weaker cells during discharge. This is claimed to enable the weaker cells to continue to supply the load, extracting some 96 percent of the entire stack capacity where passive balancing usually extracts approximately 80 percent.
On the technical side, the company advises its new device includes an integrated 6A/50V power switch, which can enable an average discharge current of 2.5A. It features an isolated balancing design that can return charge to the top of the battery stack or to any combination of cells in the stack or even to a 12V battery used as an alternator replacement.
This device is able to run off of the cell that it is discharging, which can remove the need for complicated biasing schemes. It integrates with ease via its enable pin with the company’s LTC680x family of battery stack voltage monitoring ICs without any additional software. It can also provide system telemetry, including current, resistance and temperature monitoring when used with the company’s LTC680x family of parts.
When the device is disabled, it is claimed to draw less than 20nA of quiescent current from the battery. For applications that require higher balancing current, it is possible to use multiples of these devices so that they can be paralleled. It comes in 16-lead TSSOP package and is both FMEA and ISO 26262 compliant.
The company also offers an industrial temperature version, with its LT8584IFE device that is claimed to be tested and guaranteed to operate from a -40°C to 125°C operating junction temperature. In addition, an automotive temperature version is available with, its LT8584HFE, which is also said to be tested and guaranteed to operate from a -40°C to 150°C operating junction temperature.
Linear Technology Corporation
