Functional Safety for Battery Monitoring Integrated Circuits 2017-01-1202
The Battery Monitoring Integrated Circuit (BMIC) is a key technology for Battery Electronics in the electrification of vehicles. Generally speaking, every production hybrid, plug-in hybrid, and battery electric vehicle uses some type of BMIC to monitor the voltage of each lithium battery cell. In order to achieve Functional Safety for the traction battery packs for these electrified vehicles, most designs require higher ASIL ratings for the BMIC such as C or D. For the entire market of available BMIC’s, there is a generic feature set that can be found on almost every IC on the market, such as a front end multiplexer, one or more precision references, one or more Analog to Digital (A/D) converters, a power supply, communications circuits, and window comparators. There is also a fairly consistent suite of self-diagnostics, available on just about every available BMIC, to detect failures and enable achievement of the appropriate ASIL rating. This paper provides a generic approach for the use of these BMICs which is independent of the exact vehicle application and which is applicable to BMIC’s from all vendors. The functional safety concept which can be found in Battery Controller modules across OEMs is explained. Then, the usage of diagnostic features for these BMICs is examined in detail which is the final piece necessary to understand the technical safety requirements for battery pack electronics. Special emphasis is placed on the relationship between the specific diagnostic features which are offered by the silicon suppliers, and the implementation of these technical safety requirements.