ADI's precision battery monitor family prolongs automotive battery life

These metrics are subsequently used to control battery charging and discharging profiles in order to ensure improved battery dependability and prolong battery life, while providing priority to critical functions such as engine start-up.

“Analog Devices’ ability to design mixed-signal ICs that combine precision analogue functions with digital circuitry made them the obvious choice for an integrated solution for intelligent battery sensing,” said Andreas Heim, BMW, in Germany. “This new device family replaces more expensive and less accurate solutions using multiple discrete components. Automotive system designers now have an integrated solution that better enables a level of battery management to ensure critical tasks are always performed, eliminate breakdowns due to a flat battery and help prolong battery life.”

Powered directly from the car battery, the single-chip ADuC703x devices integrate up to three 16-bit analogue-to-digital converters (ADCs), an ARM7 microcontroller, a local interconnect network (LIN) transceiver, embedded flash memory, an on-chip PGA (programmable gain amplifier) for a wide range of current measurements, on-chip attenuation resistors for direct battery voltage measurement and external or on-chip temperature sensing. Therefore, the ADuC703x precision battery monitors offer a cost-efficient, space-saving and simpler design alternative to discrete implementations consisting of a standalone processor, LIN transceiver, low drop-out regulator (LDO) and analogue front end (AFE). As a result, the component can be located directly on the negative battery pole to provide significant cost and space savings, while simplifying overall battery monitoring system design.

The profusion of new safety, entertainment, navigation and power train systems in today's car relies on more sophisticated electronic subsystems, said Mike Britchfield, Product Line Director, Precision Signal Processing, Analog Devices. These exciting new features all improve automotive performance, but in every case demand exceptional battery management capabilities, leading to increased reliability and longer life. The level of integration provided by the ADuC703x family effectively meets these needs in a single-chip IC that is easier to use, higher performance and more cost effective than the existing patchwork solutions used today.

The ADuC703x family provides accurate, continuous measurement of battery state, even while the engine is off, while consuming as little as 300 μA in low-power mode and less than 10 mA at 10 MHz in normal operating mode. The devices’ 16-bit sigma-delta ADCs measure battery voltage (direct connection, no external attenuation required) in the range of 3.5- to 18-V and battery current from less than 1 mA to 1500 A. Combined with an on-chip PGA and a temperature sensor input, the ADuC703x allows the system integrator to determine the battery’s SOC and SOH using a proprietary algorithm that resides in the monitor chip’s flash memory. The information is then communicated via the on-chip LIN 2.0 (slave) compliant transceiver to the ECU (electronic control unit).

The new battery monitor family includes a dual-ADC version (ADuC7030/3) that monitors voltage and temperature in series and a version equipped with three ADCs (ADuC7032) that allows simultaneous voltage and temperature monitoring. All of the ADCs have an 8-kHz maximum conversion rate. The current-measuring ADC has a fully differential buffered input, the ability to independently monitor battery current in power-down mode and noise performance of 60 nV rms at low conversion rates. An on-chip FIFO (ADuC7032 only) can store multiple voltage and current conversions when the core is busy.

The processing engine at the core of the ADuC703x series is an ARM7TDMI with a core clock rate that is programmable to a maximum of 20 MHz. The parts can be programmed (in-circuit) via a JTAG (Joint Test Action Group) or LIN interface, with flash storage retention of 20 years at 85 degrees C. The new devices support a maximum power supply of 33 V with all specifications applying over the range of 3.5 V to 18 V.