Renesas Electronics' New Li-ion Battery Management IC Extends Battery Life

Renesas Electronics, a global leading supplier of semiconductor solutions, recently announced the launch of the fourth-generation lithium-ion battery management chip, providing high accuracy and service life. The ISL78714 provides accurate cell voltage and temperature monitoring, as well as cell balancing and extensive system diagnostics to protect 14-cell lithium-ion battery packs while maximizing battery life and range in hybrid and electric vehicles (HEV/MHEV/PHEV/BEV).

“The ISL78714 battery management IC enables the battery management system to have best-in-class battery pack monitoring accuracy, fast data acquisition and fault detection functions. We cooperated with Mahindra Racing in Formula E technology and helped them win the race. We co-designed the lithium-ion battery management system using ISL78714 IC and RH850 MCU for Mahindra electric racing car.” said Niall Lyne, senior director of marketing and applications for automotive mixed-signal/power and video products at Renesas Electronics.

The feature-rich ISL78714 monitors and balances up to 14 strings of connected cells, measuring with an accuracy of ±2mV over the automotive operating temperature range, helping system designers make 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 provides 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 safety, reliability and high performance requirements of all types of EV battery pack systems, including HEV/PHEV, enabling automakers to achieve ISO26262 Automotive Safety Integrity Level (ASILD) assessments. In addition, the ISL78714 can monitor and read the overvoltage/undervoltage, temperature, open circuit status and fault status of 112 cells within 10ms; or monitor and read the status of 70 cells within 6.5ms.

Multiple ISL78714s can be connected together through a proprietary daisy chain to support systems of up to 420 units (30 ICs), providing industry-leading transient and EMC/EMI immunity that exceeds automotive requirements. The ISL78714 daisy chain architecture uses low-cost capacitor or transformer isolation, or a combination of both, to stack multiple battery packs together using twisted pair wiring while protecting against hot swap and high voltage transients. A watchdog timer automatically shuts down the daisy chain IC when communication with the main MCU is lost.

Key features of the ISL78714 battery management IC:

Monitor and manage up to 14 cell voltages with a measurement accuracy of ±2mV

Rugged two-wire daisy chain communication system using capacitor or transformer coupling up to 1 Mbps

Fully differential battery input range ±5V, meeting the measurement requirements of fuel cells and busbar aging battery packs

±6mV @ ±6σ 15-year board level accuracy (long-term drift)

Battery voltage and temperature measurement with high diagnostic coverage

AEC-Q100 Grade 2 compliant, operating temperature range -40°C to +105°C

The battery management system (BMS) reference design includes five ISL78714 ICs and one RH850/P1M MCU to form a complete 70-cell external balancing evaluation platform. The reference design kit provides setup and data logging via CAN and UART. A GUI, Altium layout files, and low-level drivers for the RH850 and ISL78714 are also provided. Hardware, software, and interface reference manuals and EMC reports are provided. Overall, the reference design kit enables electric vehicle system designers to easily port their software to the RH850 MCU and expand to any battery pack, saving a year of development time.

Volume production quantities of the ISL78714 Li-ion battery management IC are available now in a 64-lead TQFP package.