Battery management IC extends battery cell life for EVs

By Gina Roos, editor-in-chief

Renesas Electronics Corp. claims unmatched lifetime accuracy with its fourth-generation lithium-ion (Li-ion) battery management IC for hybrid and electric vehicles. The ISL78714 provides accurate cell voltage and temperature monitoring, cell balancing, and extensive system diagnostics to protect 14-cell Li-ion battery packs. These features help to extend the driving time and range for HEVs/MHEVs/PHEVs/BEVs.

The ISL78714 monitors and balances up to 14 series connected cells with ±2 mV accuracy across automotive temperature ranges. This enables system designers to make informed decisions based on absolute voltage levels. The device also features a precision 14-bit analog-to-digital converter and associated data acquisition circuitry; up to six external temperature inputs (two available from GPIOs), and fault detection and diagnostics for all key internal functions.

The ISL78714 monitors and reads back over/under voltage, temperature, open wire conditions, and fault status for 112 cells in less than 10 ms, or 70 cells in 6.5 ms.

Multiple ISL78714’s can be connected together via a proprietary daisy chain that supports systems up to 420 cells (30 ICs). A watchdog timer automatically shuts down a daisy-chained IC if communications is lost with the master MCU.

Key features include:

• Monitors and manages up to 14 cell voltages with ±2 mV measurement accuracy
• Two-wire daisy chain communications system using capacitor or transformer coupling up to 1 Mbits/s
• Fully differential cell input range of ±5 V accommodates fuel cell and bus bar measurement requirements for aging battery packs
• High diagnostic coverage for cell voltage and temperature measurements
• AEC-Q100 Grade-2 qualified and specified for operation from -40°C to 105°C

A battery management system (BMS) reference design is available, which includes five ISL78714 ICs and a RH850/P1M MCU to form a complete 70-cell evaluation platform for external balancing. It also provides a GUI, Altium layout files, and low-level drivers for the RH850 peripherals and ISL78714. Hardware, software, and interface reference manuals are included with an EMC report. Renesas estimates that the reference kit enables system designs to save up to one year of development time. The ISL78714 (64-lead TQFP package) is available in volume production.