12-cell Li-ion battery monitor for EV/HEV protection

June 21, 2016 // By Graham Prophet
An automotive-grade battery monitor and battery manager enable ASIL-D compliant systems; Intersil’s ISL78610 12-cell lithium-ion (Li-ion) battery pack monitor provides cell balancing and accurate voltage and temperature monitoring to safeguard Li-ion battery packs in hybrid electric vehicles, plug-in hybrid electric vehicles, and electric vehicles.

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

 

The ISL78610 monitors and balances up to 12 cells with accurate 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 analogue-to-digital converter and registers for control and data, connecting directly to a microcontroller through its 2 Mbps SPI interface. The device has four external temperature inputs, and includes fault detection and diagnostics for all key internal functions.

 

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 industry-leading transient and EMC/EMI immunity, which exceeds 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.

 

Features of the ISL78610 include;

• Monitors up to 12 cell voltages with ±10 mV measurement accuracy

• VBAT measurement accuracy ±100 mV

• 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

• 2 Mbps SPI interface provides communication with microcontroller

• AEC-Q100 Grade-2 qualified for operation from -40°C