New reference design develops highly accurate automotive smart battery sensor technology

Austrian microelectronics, a leading supplier of high-performance analog ICs and sensors , has announced the launch of an Intelligent Battery Sensor reference design for automotive applications based on the company's highly accurate AS8515 data acquisition front end.

The intelligent battery sensor (IBS) from ams is designed to monitor the state of charge (SOC) and battery safety (SOH) of the latest lithium iron phosphate automotive batteries and traditional AGM (lead acid) batteries. The IBS uses the AS8515 as the measurement front end, which can accurately and in real time measure the battery current and voltage, the temperature of the circuit board, and output these data as electronic signals. The measurement data is processed by the Fujitsu ARM Cortex-M3 microcontroller to provide accurate readings for any type of 12V battery.

The reference design is available now with full documentation as part of a development kit, is production-ready and may be selected by car manufacturers as a ready-made template for an IBS system. Unlike fixed-architecture integrated systems offered by competitors, austriamicrosystems' reference design allows users to freely choose the microcontroller.

The software provided with the austriamicrosystems IBS reference design demonstrates how to perform SoC calculations using the coulomb counting method and calculate the resulting battery impedance when the current load changes by more than 5A. The software can be easily exported to any microcontroller of the developer's choice, including other ARM Cortex-M series devices. The AS8515 includes an integrated LIN transceiver and IBS sensor module that can act as a LIN slave in an automotive system . The reference design includes a standalone LIN motherboard with a LIN controller and a USB controller, allowing developers to control and configure the sensor module through austriamicrosystems' graphical user interface (for Windows operating system computers) .

The IBS module combines the expertise of Austrianmicrosystems in high-precision and high-sensitivity analog circuits to perform extremely accurate battery measurements: the current measurement accuracy error is ±0.5% (typical) over the entire signal range; the voltage measurement accuracy error is less than ±0.1% (typical) over the temperature range of -40°C to +115°C. The linearity deviation is less than 0.01%.

The highly efficient ARM Cortex-M3 core within the Fujitsu MB9B520K microcontroller helps to significantly reduce energy consumption, with the entire sensor module consuming only 8mA in normal operation and just 87µA in standby mode in current monitoring mode.

“Competitors’ IBS systems offer fixed architecture systems to automakers, forcing them to use outdated microcontrollers in their system packages,” said Bernd Gessner, Vice President and General Manager of the Automotive Business Unit at ams. “ams’ approach is advantageous because we decouple the sensor from the microcontroller, allowing developers to always use the latest microcontrollers in their IBS designs while using ams’ proven measurement front end.”