Charge is transferred using a lower capacity battery that is sequentially connected across the batteries in the stack. Not only does this battery transfer charge, but the energy in the transfer battery adds to the total energy in the stack, thus increasing capacity. Included on the chip is sequencing, drive circuitry for high voltage external NFETs, voltage monitoring and protection. The LTC3305 is designed for stand-alone operation and does not require a microprocessor or other control circuitry. With the LTC3305, one battery in the stack can be replaced and quickly balanced to the remaining batteries. Use it in applications such as telecom backup systems, home battery-powered backup systems, electric vehicles and industrial lighting systems.
LTC3305 employs an auxiliary battery storage cell to transfer charge to or from each individual battery in the stack. A mode pin provides two operating modes: timer mode and continuous mode. In timer mode, once the balancing operation is completed, the LTC3305 goes into a low power state for a programmed time and then periodically rebalances the batteries. In continuous mode, the balancing operation continues even after the batteries are balanced to their programmed termination voltage. Additional devices can be stacked to balance higher voltage series battery packs.
The LTC3305 occupies a thermally-enhanced low profile (0.75-mm) 38-lead TSSOP package. The E and I grades are specified with operating junction temperature range of -40°C to 125°C. Pricing starts at $6.95 (1000).
Linear Technology; www.linear.com/product/LTC3305