Li-ion battery pack monitor safeguards traction battery systems

June 20, 2016 // By Christoph Hammerschmidt
Monitoring voltage and temperature in traction batteries is essential to keep these batteries in best shape and to fire. The ISL78610 battery pack monitor from Intersil helps design engineers achieving these tasks: The IC can concurrently measure balance, voltage and temperature in lithium-ion battery packs with up to twelve cells. It also can be combined with the ISL78600 multi-cell battery manager.

System designers can use the ISL78610 as a standalone battery-pack monitor or as a redundant back-up device when combined with the ISL78600. This combination enables automobile manufacturers to achieve the higher ISO 26262 automotive safety integrity level (ASIL) D rating.

The feature-rich ISL78610 monitors and balances up to 12 cells with voltage readings and diagnostics. This lets system designers make informed decisions based on absolute voltage levels rather than simply receiving a “system not OK” signal indicating an out-of-range condition. The ISL78610 includes a voltage reference, 14-bit A/D converter and registers for control and data, while connecting directly to a microcontroller through its 2Mbps SPI interface. The device also offers four external temperature inputs, and includes fault detection and diagnostics for key internal functions.

With such features, the battery monitoring and management ICs meet the stringent safety, reliability and performance requirements of next generation automotive battery pack systems. Together, the ISL78610 and ISL78600 offer internal and external fault detection such as open wire, over and under voltage as well as temperature and cell balancing faults to mitigate battery pack failures. Multiple devices can be daisy-chained together to support systems with up to 168 cells using a proprietary communications system that provides transient and EMC/EMI immunity, typically exceeding carmaker requirements. Intersil’s daisy-chain architecture uses low-cost capacitive isolation with twisted pair wiring to stack multiple battery packs together, while the ICs internal protection guards against hot plug and high voltage transients. A watchdog timer automatically shuts down a daisy-chained IC if communications is lost with the master microcontroller.

Key Features and Specifications of ISL78610

  • Monitors up to 12 cell voltages with ±10mV measurement accuracy
  • VBAT measurement accuracy ±100mV
  • Measures absolute voltage rather than preset voltage levels
  • Internal and four external temperature monitoring inputs
  • Watchdog timer shuts down device if communications is lost with master controller
  • Integrated system diagnostics for all key internal functions
  • 2Mbps SPI interface provides communication with microcontroller
  • AEC-Q100 Grade-2