The Freescale MC33771 battery cell controller and its sister product, the MC33664 isolated communication interface, equipped with 14 cell balancing transistors, a current sensor with ±0.5% accuracy from milliamperes to kiloamperes, and a 2Mbps communication transceiver integrated into a single 64-pin QFP package, provide robust and reliable performance for 48V battery systems, enabling economical scalability beyond 1000V. The solution's built-in diagnostics protect automotive and industrial battery packs from catastrophic fault conditions, and because it utilizes transformer-based isolated high-speed transceivers, it eliminates the need for costly isolated CAN buses to meet ASIL-C requirements. Furthermore, thanks to these capabilities, the solution is suitable for a wide range of automotive and industrial applications, including 48V battery packs, hybrid and electric vehicles, electric bicycles, and energy storage systems.

Automotive and industrial batteries are facing increasing pressure due to new key applications, so issues such as overcharging, overheating, internal short circuits, or overloads must be addressed to ensure a safe operating environment. Therefore, it is important for battery cell controllers to accurately measure differential cell voltage, temperature, and current to provide precise and reliable battery diagnostic results. In addition, for overall system battery control and safety, it is also important to quickly and accurately transmit this information from the battery cell controller to the pack controller so that the battery's total energy can be utilized.

"The robust design and comprehensive integration capabilities of the new battery cell controller reflect Freescale's system-level approach to cost-effectively managing battery charging while preventing errors and hazardous situations," said James Bates, Executive Vice President and General Manager of Freescale's Analog and Sensor Group. "Because this new battery cell controller leverages Freescale's automotive technology and reliable, highly integrated, high-performance solutions, it reduces the cost of meeting stringent safety requirements."

The MC33771 integrates many key features necessary to control a single 48V battery pack, including the ability to accurately measure current and voltage simultaneously within 65us at 2mV intervals, allowing it to easily meet ISO 26262 ASIL-C requirements. Furthermore, embedded function verification and error diagnosis enable compliance with ISO 26262 ASIL-C functional safety standards without the need for additional external circuitry. For high-voltage systems, an integrated daisy-chained differential transceiver communicates at 2Mbps up to 3750V using the isolation characteristics of a robust transformer instead of a costly isolated CAN bus, whereas the MC33664 uses the same transformer-coupled isolation to connect the battery pack directly to the system MCU's dual SPI interface. Freescale battery cell controller solutions provide superior performance through a low system BOM (Bill of Materials) and robust system isolation for ASIL-C rated battery packs.

The MC33771, combined with Freescale's MC33664 isolated communication device, supports optimal lifecycles for various battery structures, including centralized distributed CAN and distributed daisy-chain topologies. The battery cell controller features a robust and secure high-speed daisy-chain communication design and provides services in place of the costly isolated CAN bus. The device's ability to provide services in place of CAN-based solutions eliminates the need for local microcontrollers, voltage regulators, and isolated CAN layers within the battery, thereby reducing cost and design complexity.

The MC33771, a SafeAssure functional safety solution, was developed to enable customers to easily meet stringent ISO 26262 ASIL-C requirements, along with strict standards for ESD, EMC, low current consumption, and AEC-Q100 automotive conformance design. The Freescale MC33771 can be used in various existing battery topologies and features a specific set of functions to support typical 48V LFP batteries in a single device, including 14 differential voltage measurements, 14 embedded cell balancing transistors, 7 analog inputs for temperature measurement, 1 embedded current sensor that enables the measurement of individual cell impedance synchronized with cell voltage measurements, and a Coulomb counter for enhanced State of Charge (SOC) measurement.

Additional features are as follows.

- 9.6 V ≤ VPWR ≤ 61.6 V operating voltage, 70 V transient voltage

- SPI or isolated 2MHz differential communication

- Current sensor with ±0.5% accuracy from milliamperes to kiloamperes

- 14x Differential Cell Voltage Measurement and Stack Voltage Measurement

- Synchronized cell voltage/current measurement

- Coulomb calculation

- 7x ADC/GPIO/Temperature Sensor Inputs

- Valid upon initialization

- Onboard 300mA passive cell balancing

- Low-levelPower mode

- 64-pin QFP package

Supply situation and prices

The MC33771 and MC33664 devices are currently available as samples; production for the industrial market is scheduled for the first quarter of 2015, and for the automotive market in the third quarter of 2015. The suggested retail price for the MC33771 is projected to be between $4.86 and $10.95 for the 10kU model. The suggested retail price for the MC33664 is projected to be $1.65 for the 10kU model. Additional derivative products are also scheduled for release in 2015. Further details can be found at http://www.freescale.com/Battery.

Freescale supplies hardware supporting the MC33771 battery cell controller and MC33664 transformer physical layer, along with the KIT33771ASP1EVB and KIT33664EVB evaluation kits. These boards are designed to shorten time-to-market and demonstrate the advantages provided by the device's various embedded functions.

Powerful and stable analog performance

Most Freescale analog products meet the requirements of key automotive and industrial markets, including operation over a wide temperature range. These products are designed, manufactured, and verified through rigorous process control using industry-standard methodologies designed to yield failure rates that meet the most stringent requirements of the automotive and industrial markets. The MC33771 and MC33664 devices are included in Freescale’s product life extension program, which guarantees a supply of at least 10 or 15 years from the time of release. Terms and conditions and a list of applicable Freescale products can be found at www.freescale.com/productlongevity.