Battery-pack controller manages 14-cell lithium ion sources to ASIL-C

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By eeNews Europe

The integrated 14-cell lithium-ion battery cell controller is aimed at industrial and automotive applications, designed to cost effectively meet the stringent requirements for ASIL-C functional safety. With 14 cell balancing transistors, a current sensor with ±0.5% accuracy from milliamps to kiloamps, and 2 Mbps communication transceiver interface integrated into a single 64-pin QFP package, the MC33771 battery cell controller and companion MC33664 isolated communications interface handle 48 V battery systems, enabling economical scalability beyond 1000V.

Built-in diagnostics help protect automotive and industrial battery packs against critical fault conditions, and its transformer-coupled isolated high speed transceiver eliminates the need for expensive isolated CAN buses to meet ASIL-C requirements. Together, these features suit the products to a range of range of automotive and industrial applications including 48V battery packs, hybrid and electric cars, E-bikes and energy storage systems.

A battery cell controller must provide precise and reliable battery diagnostics by accurately measuring differential cell voltages, temperatures and currents. It is equally critical that this information be communicated quickly and accurately from the battery cell controller to the pack controller for system-wide control and safety of the battery, allowing the full energy content of the battery to be utilised. The MC33771 incorporates the capability to synchronously measure currents and voltages with 2 mV accuracy within 65 µsec, making it easier to meet ISO 26262 ASIL-C requirements. Embedded functional verification and fault diagnostics enable compliance with ISO 26262 ASIL-C functional safety standards without additional external circuitry.

For higher voltage systems, the integrated daisy chain differential transceiver communicates at 2 Mbps using transformer coupled isolation up to 3750V, while the MC33664 connects the battery pack directly to the system MCU’s dual SPI interface using the same transformer coupled isolation.

The battery cell controller uses a daisy-chain communication design that serves as a replacement for isolated CAN busses. The MC33771, a SafeAssure functional safety solution, has been developed to enable designs to meet stringent ISO 26262 ASIL-C requirements, as well as rigorous standards for ESD, EMC, low current consumption and AEC-Q100 automotive qualified design. While the MC33771 is usable across most known battery topologies, it features a specific feature set to address a typical 48 V LFP Battery with one device that includes 14 differential voltage measurements, 14 embedded cell balancing transistors, seven analogue inputs for temperature measurement, one embedded current sensor that synchronises with the cell voltage measurements to allow determination of individual cell impedance, and a coulomb counter for enhanced state of charge determination. There is onboard 300 mA passive cell balancing.



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