Battery management chip maximizes cell life, driving range
The feature-rich ISL78714 monitors and balances up to 14 series connected cells with ±2mV accuracy across automotive temperature ranges, letting system designers make informed decisions based on absolute voltage levels. The ISL78714 includes a precision 14-bit analog-to-digital converter and associated data acquisition circuitry. The device also offers up to six external temperature inputs (two available from GPIOs) and includes fault detection and diagnostics for all key internal functions.
The ISL78714 meets the stringent reliability and performance requirements of battery pack systems for all EV variants including HEV/PHEV, with safety features enabling automotive manufacturers to achieve the ISO 26262 automotive safety integrity level (ASIL D). In addition, the ISL78714 monitors and reads back over/under voltage, temperature, open wire conditions, and fault status for 112 cells in less than 10ms, or 70 cells in 6.5ms.
Multiple ISL78714’s can be connected together via a proprietary daisy chain that supports systems up to 420 cells (30 ICs) that provide industry-leading transient and EMC/EMI immunity, exceeding automotive requirements. The ISL78714’s daisy-chain architecture uses low-cost capacitive or transformer isolation, or a combination of both, with twisted pair wiring to stack multiple battery packs together while protecting against hot plug and high voltage transients. A watchdog timer automatically shuts down a daisy-chained IC if communications is lost with the master MCU.
The battery management IC is already in use in Mahindra’s Formula E race cars. Renesas is a technology partner of Mahindra. “Together, we designed and integrated a low-voltage Li-ion battery management system featuring ISL78714 ICs and RH850 microcontrollers in Mahindra Racing electric race cars,” said Niall Lyne, Senior Director of Product Marketing and Applications, Automotive Mixed-Signal/Power and Video at Renesas.
A battery management system (BMS) reference design is available, which includes five ISL78714ICs and a RH850/P1M MCU to form a complete 70-cell evaluation platform for external balancing. The reference design kit provides setup and data logging via CAN and UART. Also provided is a GUI, Altium layout files and low-level drivers for the RH850 peripherals and ISL78714. Hardware, software, and interface reference manuals are included, along with an EMC report. Together, the reference design kit makes it easy for electric vehicle system designers to port their software to the RH850 MCU, scale to any battery pack size, and save up to one year of development time.
More information: www.renesas.com/products/isl78714.
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