Lead-acid automotive batteries can be replaced by Li-ion chemistries to reduce weight, increase reliability and boost energy efficiency for engine start-stop systems and energy recuperation technologies. Recent advances in Li-ion battery chemistry for cold temperature operation and cold cranking power now enable Li-ion batteries to displace lead-acid even as the starter battery.

As a result, the inherent challenges of overcharge, overheating and internal short circuit are increasingly managed by electronics. To maintain safe operating conditions and ensure system-wide control of the battery, next-generation battery cell controllers like Freescale’s must provide accurate, reliable battery diagnostics and high speed communication of status.

Freescale’s new MC33772 battery cell controller supports this paradigm shift, providing a single-chip solution optimized for all critical performance and safety duties, and featuring robust functional verification supporting ISO 26262 ASIL-C requirements, which help protect automotive and industrial battery packs against critical fault conditions. Higher level ASIL-D system implementations can also be realized using multiple Freescale battery cell controllers for redundancy.

Drivers face a host of issues and concerns about their lead-acid batteries, many of which are caused by outside elements like extreme temperatures that are hard to control, causing about 100 million batteries to be replaced every year in the US alone. With the expansion of our broad portfolio of battery cell controllers, Freescale is helping reduce those concerns, making it easier for our customers to offer an effective Li-ion alternative to lead-acid, while meeting stringent performance and functional safety requirements across a wide variety of battery sizes and types.

—James Bates, senior vice president and general manager for Freescale’s Analog & Sensors Group

In addition to 14V Li-ion battery packs, the MC33772 product’s optimized feature set is well suited for reducing system electronics BOM cost in a broad range of automotive and industrial battery management applications, including 48V battery systems, high voltage hybrid and electric cars, E-bikes and energy storage systems.

The MC33772 delivers a balance of measurement accuracy, scalability and high speed isolated communications. It supports rapid, 2Mbps communication of battery health and conditions for a variety of battery management system topologies, including centralized, distributed CAN and distributed daisy chain systems.

Key features include:

• Available in 3, 4, 5 and 6 cell versions
• 5V (SPI)/7V (TPL) ≤ VPWR ≤ 30 V operation, 40 V transient
• SPI or isolated 2 MHz differential communication using MC33664 TPL
• Current sensor with ±0.5% accuracy from milliamps to kiloamps
• 6x differential cell voltage measurement and stack voltage measurement
• Synchronized cell voltage/current measurement
• Coulomb counting
• 7x ADC/GPIO/temperature sensor inputs
• Addressable on initialization
• 6x onboard 300 mA passive cell balancing drivers w/ dedicated timers
• Low-power modes
• 48-pin QFP package

The MC33772 is engineered to help customers easily meet stringent ISO 26262 ASIL-C requirements through integrated functional verification and advanced diagnostic features in single-chip. An ASIL-D system level implementation is also possible with Freescale battery cell controllers, allowing customers to meet multiple functional safety concepts and address safety system level requirements. As a Freescale SafeAssure functional safety solution, this portfolio meets standards for ESD, EMC, low current consumption and AEC-Q100 automotive qualified design.

(The Freescale SafeAssure functional safety program is designed to help system manufacturers more easily achieve system compliance with functional safety standards: International Standards Organization (ISO) 26262 and International Electrotechnical Commission (IEC) 61508.)

Freescale offers hardware to support the MC33771 and MC33772 battery cell controllers and the MC33664 transformer physical layer with the KIT33771ASP1EVB, KIT33772ASP1EVB and KIT33664EVB evaluation kits. These boards are engineered to accelerate time-to-market and demonstrate the benefits of the multiple embedded functions of the products.

The MC33771, MC33772 and MC33664 products are sampling now. The MC33771 and MC33664 products are expected to be in production by Q4 2015, while the MC33772 product is planned for production by Q2 2016. The MC33771 will be available for a suggested retail price starting at US$4.86 in 10kU quantities, and the MC33772 will be available for a suggested retail price starting at $US3.46 depending on cell count and feature set. The MC33664 will be available for a suggested retail price of US$1.65 in 10kU quantities.