Electric vehicle battery management (BMS) system solution based on ST L9963-EEWORLD

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As new energy vehicles are developing around the world, lithium battery electric vehicles have become the most mainstream development direction. In lithium battery electric vehicle technology, in addition to how to effectively improve motor power and efficiency, battery energy management is a very important part

An automotive battery management system ( BMS ) must be able to meet key functions such as voltage, temperature and current monitoring, battery state of charge (SoC), and cell balancing for lithium-ion (Li-ion) batteries.

In fact, the main functions of electric vehicle battery management system are:

Battery protection to prevent operation outside of its safe operating area. Battery monitoring by estimating the pack state of charge (SoC) and state of health (SoH) during charge and discharge. Battery optimization to extend battery life and capacity through cell balancing, thus optimizing the driving range of hybrid (H EV ), plug-in (PH EV ) and full electric vehicles (B EV ).

New highly integrated solutions for your automotive BMS design, STMicroelectronics battery management system solutions for automotive applications are designed to meet all these demanding design requirements. Based on the new highly integrated battery management IC L9963 and its companion isolated transceiver L9963 T, our solution is able to provide the highest accuracy measurement of up to 14 series cells in a single daisy chain or bidirectional daisy chain configuration, and embed complex battery monitoring and diagnostic functions. It also meets the stringent Automotive Safety Integrity Level (ASIL) D requirements.

EVAL - L9963 -MCU is a hardware tool for the automotive chip L9963 for battery management applications. It can be used to develop a 48 V battery management system ( BMS ) or as a lower level of a distributed BMS (depending on the total battery voltage. Additional levels can be added due to EVAL-L9963-NDS).

The EVAL-L9963-MCU allows the user to connect up to 14 channels for battery voltage sensing, one channel for current sensing and up to 4 analog inputs for temperature sensing (and an additional on-board NTC to sense PCB temperature). The board comes with pre-loaded GUI firmware for the on-board microcontroller and is intended to be used with the ST SW-L9963 PC graphical user interface.

At the same time, the monitoring values are output in the form of digital signals, which requires a period of analog-to-digital signal conversion compared to the past. This can improve battery synchronization problems and can manage up to 7 external temperature sensors to strictly control battery temperature to avoid overheating.

The L9963 is a Li-ion battery monitoring and protection chip for high reliability automotive applications and energy storage systems. Up to 14 stacked cells can be monitored to meet the requirements of 48 V and higher voltage systems. Each cell voltage as well as the current with on-chip coulomb counting can be measured with high accuracy. The device can monitor up to 7 NTCs. Information is transmitted via SPI communication or an isolated interface.

Multiple L9963s can be connected in a daisy chain and communicate with a host processor through a transformer-isolated interface, featuring high-speed, low EMI, long-distance and reliable data transmission. Programmable channel selection is provided in both normal and low-power modes. Balancing can be automatically terminated based on an internal timer interrupt. Nine GPIOs are integrated for external monitoring and control. The L9963 has a comprehensive set of fault detection and notification functions to meet the requirements of safety standards.

In addition, the L9963 also complies with the ASIL-D of the ISO 26262 standard, has built-in comprehensive fault detection and notification functions for automotive safety, and also has an SPI interface and a 2.66Mbps vertical communication interface that can establish multiple L9963 high-speed communications. This 21.66Mbps vertical communication interface enables 8 chips to convert and read signals for up to 96 battery cells, and the operation time is less than 4ms, and can be combined with various types of transformers or capacitive electrical isolation combinations.

The L9963 is designed to allow hot-swap operation, which means that the external Zener diode used to protect the battery management system can be eliminated. Traditional designs do not allow hot-swap operation, so the battery cannot be shut down and must be protected with a Zener diode. This also means that the L9963 can reduce the cost of using such diodes.

The main features of L9963 are as follows:

AEC-Q100 compliant

Measure 4 to 14 cells in series with 0 us synchronization delay between samples. Bus connection is also supported without changing the results of the cells

Coulomb counter supports battery pack overcurrent detection both when the ignition is on and off. Fully synchronized current and voltage samples

16-bit voltage measurement with ±2 mV maximum error in the [1.7 – 4.7] V range over the entire operating temperature range

2.66 Mbps isolated serial communication with regeneration buffer, supporting dual access rings. Less than 2 µs delay between the start of conversion of the first and 15th device in the chain. Less than 4 ms to convert and read 96 cells in a system using 8 L9963s. Supports transformer- and capacitor-based isolation

Passive internal balancing current of 200 mA per cell in normal and silent balancing modes. Cyclic wake-up measurements can be performed. Manual/timed balancing, on multiple channels simultaneously; internal/external balancing

Completely streamlined battery measurement path with ADC swapping for enhanced safety and simplicity

Smart diagnostic routines with automatic fault verification. Fault notification via SPI Global Status Word (GSW) and dedicated fault line

Two 5 V regulators support external load connection with 25 mA (VCOM) and 50 mA (VTREF) current capabilities

9 GPIOs, up to 7 analog inputs for NTC detection

Robust hot-swap performance. No need for a Zener diode in parallel with each unit

Fully compliant with ISO26262 standard, ASIL-D system ready

TQFP64EP package

In addition, the L9963 is designed to allow hot-swap operation, which means that the external Zener diode used to protect the battery management system can be eliminated. Traditional designs do not allow hot-swap operation, so the battery cannot be shut down and must be protected by a Zener diode. This also means that the L9963 can reduce the cost of using such diodes.

The automotive-grade 32-bit MCU SPC574Sx is a next-generation microcontroller series built on the Power Architecture embedded category.

The SPC574Sx family of 32-bit microcontrollers is the latest in integrated automotive application controllers. It belongs to an extended automotive-centric family of products designed to address the next wave of chassis and safety electronics applications within the car. The advanced and cost-effective main processor core of this automotive controller family conforms to the Power Architecture embedded category and implements only the VLE (variable length encoding) APU, which improves code density. It runs at speeds up to 140 MHz and provides high-performance processing optimized for low power consumption. It leverages the available development infrastructure of current Power Architecture devices and is supported by software drivers, operating systems, and configuration code to assist users in implementation.

The main functions are as follows

AEC-Q100 compliant

High performance e200z4d dual core

32-bit Power Architecture CPU

Core frequency up to 140 MHz

Dual-issue 5-stage pipeline in-order execution core

Variable Length Encoding (VLE)

Core MPU

Floating point, end-to-end error correction

8 KB instruction cache with error detection code

32 KB local data RAM and 4 KB data cache and 8 KB instruction cache

1600 KB (1.5 MB code + 64 KB data) on-chip Flash: supports reading during program and erase operations, and multiple modules to allow EEPROM emulation

128 KB on-chip RAM (96 KB on-chip RAM + 32 KB local data RAM)

Multi-channel direct memory access controller (eDMA) with 32 channels

Comprehensive new generation ASIL D safety concept

ASILD SEooC approach (Security Element Out of Context)

FCCU is used to collect and respond to fault notifications

Memory Error Management Unit (MEMU), which collects and reports error events in memory

End-to-end error correction code (e2eECC) logic

Cyclic Redundancy Check (CRC) unit

8 enhanced 12-bit SAR analog converters

2 groups: 3 ADCs and one supervisor ADC

1.5 µs conversion time at 12 MHz

Up to 32 physical channels