Cell balancing IC recovers energy and provides charge flow monitoring

December 17, 2013 // By Graham Prophet
Making up to 96% of the energy in a battery pack usable, LT8584 is a monolithic flyback DC/DC converter that can handle 2.5A average currents, and is designed to actively balance high voltage stacks of batteries, such as are used in electric and hybrid vehicles as well as uninterruptible power supplies and energy storage systems.

LT8584 offers high efficiency active balancing, which redistributes the charge from the stronger cells (higher voltage) to charge the weaker cells during discharge. This enables the weaker cells to continue to supply the load, extracting 96% of the entire stack capacity where passive balancing usually extracts, according to Linear Technology, approximately 80%. Passive energy balancing protects against damage to cells by over-charge or deep discharge, but offers no improved run-time as it dissipates the added energy of the higher capacity batteries to match the lowest one.

The device includes an integrated 6A/50V power switch, enabling an average discharge current of 2.5A while offering a simple and compact application circuit. Its isolated balancing design 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.

The LT8584 takes its own power from the cell that it is discharging, removing the need for complicated biasing schemes. It integrates seamlessly via the enable pin with the LTC680x family of battery stack voltage monitoring ICs without any additional software. The LT8584 also provides system telemetry, including current, resistance and temperature monitoring when used with the LTC680x family of parts. When the LT8584 is disabled, it draws less than 20 nA of quiescent current from the battery. For applications that require higher balancing current, multiple LT8584s can be paralleled. It is packaged in a 16-lead TSSOP and is both FMEA and ISO 26262 compliant.

The LT8584EFE is packaged in 16-lead TSSOP and is priced starting at $2.95 (1000). An industrial temperature version, the LT8584IFE is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and is priced starting at $3.25 (1000). An automotive temperature version, the LT8584HFE is tested and guaranteed to operate from a -40°C to 150°C operating junction temperature and is priced starting at $3.50 (1000).

Linear Technology; www.linear.com/product/LT8584