Linear Technology bi-directional multicell active balancer for series-Connected battery stacks

Linear Technology Corporation announced the LTC3300-1, a high efficiency bidirectional multicell battery balancer for equalizing cell state of charge (SoC) in a series-connected battery stack. With this IC, applications such as electric vehicles (EVs), plug-in hybrid EVs and large energy storage systems using cells with mismatched capacities are no longer limited by the lowest capacity cell in the stack. The device goes beyond purely dissipative passive balancing solutions, enhancing battery performance by efficiently transferring charge to or from adjacent cells in order to bring mismatched cells into SoC balance within the stack. By redistributing charge throughout the stack, the IC compensates for lost capacity due to the weakest cells, enabling faster charging and extending the run time and usable lifetime of the battery stack.

The data sheet for this device is a tutorial in itself. It contains fault protection information critical in these types of high-energy source systems as well as Failure mechanism effect analysis charts with Scenario-Effect-Design mitigation suggestions. Battery interconnection integrity is also outlined.

Summary of Features: LTC3300-1

• Bidirectional Synchronous Flyback Balancing of up to 6 Li-Ion or LiFePO4 Cells in Series
• Up to 10A Balancing Current (Set by External Components)
• Bidirectional Architecture Minimizes Balancing Time & Power Dissipation
• Up to 92% Charge Transfer Efficiency
• Stackable Architecture Enables >1000V Systems
• Uses Simple 2-Winding Transformers
• 1MHz Daisy-Chainable Serial Interface with 4-Bit CRC Packet Error Checking
• High Noise Margin Serial Communication
• Numerous Fault Protection Features

48-Lead 7mm x 7mm Exposed Pad QFN & LQFP Packages

LTC3300-1/LTC6803-1 typical battery management system (BMS)

Control of each balancer is provided via a unique level-shifting SPI-compatible serial interface which enables multiple LTC3300-1 devices to be connected in series, without optocouplers or isolators. The part’s stackable architecture together with interleaved transformer connections enable efficient balancing of every cell in an arbitrarily tall string (>1000V) of series-connected batteries. All associated gate drive circuitry, precision current sensing, fault protection circuitry and a robust serial data interface with built-in watchdog timer and cyclic redundancy check (CRC) data error checking are integrated.

The device is offered in thermally enhanced surface-mount compatible packages: a low profile (0.75mm) 48-lead 7mm x 7mm QFN and a 48-pin 7mm x 7mm LQFP package. The I grade is specified for both packages, with operating junction temperature range of -40°C to +125°C. 1,000-piece pricing starts at $5.95.

For more information visit Linear Technology’s website