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Battery managers promise high accuracy, device safety

Posted: 15 Oct 2008 ?? ?Print Version ?Bookmark and Share

Keywords:battery manager? Li-ion battery? portable device safety?

Combining its patented high voltage manufacturing process and AVR MCU technology, Atmel Corp. has developed a family of single-chip Li-ion battery management devices that offers high analog accuracy at low power consumption, while ensuring that portable handheld applications have all the necessary safety functions.

While portable devices offer high energy density, low weight and volume, they require careful monitoring and charging control to ensure safety and optimum life time. Safety is a major criterion for battery usage and recent industry problemsgenerating huge recalls from manufacturersillustrates the importance of safe and accurate control functions. This also includes the need for authentication to ensure the user will use a certified battery and not a copy that can potentially be unsafe.

Atmel has been working with key battery manufacturers to develop optimized solutions and is now offering a full range of MCUs dedicated to Li-ion battery management supporting 1 to 4 cells. This product family offers a unique set of features to optimize performance and safety.

By giving extremely accurate voltage measurements, it is possible to control the charge and discharge cut-off voltages more accurately, thus making it possible to use up to 15 percent extra energy of the battery compared to less accurate solutions while maintaining all safety requirements. The accuracy is achieved using Atmel's patented method for calibrating the voltage reference in conjunction with high resolution delta sigma ADCs for voltage measurement.

The family consists of 6 devices targeting different end markets. The ATmega4HVD and ATmega8HVD target the low-end consumer market requiring protection and authentication. For applications requiring gas gauge, the ATmega8HVA and ATmega16HVA are the ideal products, while the ATmega16HVB and ATmega32HVB targets the notebook battery market. All parts are single chip battery side solutions incorporating a protection with high-side N-channel FET drivers.

Support kits
Atmel has designed reference design kits showing how to build a complete battery pack using the new AVR battery management devices. The reference design kits include complete firmware and provide all needed safety measures for a Li-ion battery design. This includes over- and under-voltage protection and protection against excessive charge and discharge currents. The reference designs also features high accuracy voltage and current measurements, temperature checks, communication interface with command set based on battery specification, authentication and gas gauging.

To evaluate the performance of the reference designs, they are supported with the SB200 evaluation board. This board includes Li-ion batteries, a programmable charger and load, and a USB communication gateway between the reference kits and a PC. The SB200 connects to AVR Studio by starting the AVR battery management services plug-in. Through this interface all battery parameters can be observed and modified, and the ATAVRSB200 functions are also controlled through this interface.

The ATmega8HVA and ATmega16HVA, in 36-pin LGA and 28-pin TSOP packages, are in currently in production. Engineering samples of the ATmega8HVD in 28-pin DFN packages are available, while the ATmega4HVD, ATmega16HVB and ATmega32HVB will be sampling in Q1 09.

Prices start at $0.95, $1.14, $2.08 and $2.49 in 10,000 quantity pieces for ATmega4HVD, ATmega8HVD, ATmega8HVA and ATmega16HVA, respectively.

The ATmega8HVA and ATmega16HVA are supported by the SB201 reference design (ordering number: ATAVRSB201) that is available at $139. The ATmega8HVD is supported by the SB204 reference design (ordering number: ATAVRSB204) that will be available from October 2008 at $99. The SB200 evaluation kit (ordering number: ATAVRSB200) is available at $199.

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