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One-chip solutions monitor car battery state-of-charge

Posted: 26 Oct 2006 ?? ?Print Version ?Bookmark and Share

Keywords:Analog Devices? ADuC7030? ADuC7033? ADuC7032? Smart Battery Sensors?

Analog Devices' ADuC703x family of Smart Battery Sensors, claiming the first single-chip solution for precision battery management in automotive applications, integrates high-precision data acquisition of current, voltage and temperature, a programmable flash memory-based MCU, and a LIN-based controller with high-voltage transceiver, all in a small 48-pin package.

Car electronics failures
Sixty percent of all automotive electronics failures can be attributed to faulty or discharged batteries in high-end cars, according to the Allgemeiner Deutscher Automobil-Club. Addressing the issues of critical functionality and longer battery life, this monitor facilitates accurate determination of battery state-of-charge and overall condition, and better control of charging and discharging profiles in order to extend battery life. Early-warning diagnostics with appropriate feedback keeps the user in the loop when it comes to maintaining a proper battery-servicing schedule.

Powered directly from the car battery, the chip, which is designed for placement right at the battery's negative pole, integrates a programmable front-end amplifier, up to three 16bit ADCs, an ARM7 MCU, a LIN transceiver, embedded flash memory, on-chip attenuation resistors for direct battery voltage measurement, and external or on-chip temperature sensing.

The dedicated (i.e., non-multiplexed) dual/triple 16bit sigma-delta ADCs measure battery current, voltage and temperature. The output data from these blocks defines the battery's state-of-charge (SOC) and overall condition (i.e., its so-called state-of-health, SOH). These metrics are subsequently used to control battery charging and discharging profiles in order to maximize battery reliability and prolong life. The chip's flash-memory-based ARM7 MCU, versus earlier ADuC8000-based systems, maximizes processing power.

In standard operation, the ADuC703x continuously monitors the battery state, even while the engine is off. Quiescent current draw is as little as 300?A in the low-power mode and less than 10mA at 10MHz during normal operation. The 16bit sigma-delta ADCs, working from the input stages, measure battery voltage (direct connection, no external attenuation required) over the range of 3.5-18V and battery current from less than 1A to 1500A. The SOC and SOH are then determined from a proprietary algorithm that resides in the monitor chip's flash memory. The resulting output is transmitted to the auto's electronic control unit (ECU) via the chip's LIN 2.0 (slave) compliant transceiver.

Voltage, temperature monitor
The two-ADC ADuC7030/3 monitors voltage and temperature in series; the three-ADC ADuC7032 allows simultaneous voltage and temperature monitoring. All of the ADCs have an 8kHz maximum conversion rate. The current-measuring ADC has a fully differential buffered input, and can independently monitor battery current in power-down mode. 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 20MHz. The parts can be programmed (in-circuit) via a JTAG or LIN interface, with flash storage retention of 20 years at 85C. The devices are rated for operation up to 33V; all device specifications apply over the range of 3.5-18V.

The devices, available in a 7-by-7mm LFCSP and/or LQFP and rated for operation over -40C to 125C, are priced at $6.73 each for the ADuC7030, $7.10 for the ADuC7033, and $7.55 for the ADuC7032, all in 1,000 quantities. All devices in the ADuC703x family are sampling today with full production scheduled for November.

- Vince Biancomano

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