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AVR MCU implements smart battery monitoring in one chip

Posted: 04 Feb 2005 ?? ?Print Version ?Bookmark and Share

Keywords:atmel? atmega406? avr? microcontroller? mcu?

The ATmega406 is touted by Atmel Corp. to be the first high-voltage technology AVR microcontroller (MCU) implementing full 2-4 cell Li-ion smart battery monitoring and protection on a single chip.

To enable the new MCU to be powered directly from a 2-, 3- or 4-cell Li-ion configuration, the device includes an on-chip voltage regulator that allows it to be powered from 4V to 25V. It also features three 25V-tolerant FET drivers for charge, discharge and pre-charge, as well as on-chip FETs for cell balancing. And to provide the most accurate estimate of charge left, Atmel added, the device has a Coulomb Counter ADC with an 18bit output for battery current monitoring as well as a 12bit ADC for individual cell voltage and temperature monitoring. Both ADCs use high-accuracy on-chip voltage reference.

"The ATmega406 is a result of Atmel's smart battery R&D program since early 2001. Long-term development in cooperation with battery manufacturers has resulted in this device integrating all battery management features on one chip," shared Morten Reintz, Marketing Manager for the company's Smart Battery technology.

"This second generation smart battery chip from Atmel enables battery manufacturers to get longer battery life and significantly more accurate estimate of charge left at a lower cost than earlier solutions," Reintz added.

An independent circuitry

Battery protection is implemented as independent circuitry, not requiring the MCU to operate. If the device is exposed to an over-current or short-circuit condition, the autonomous battery protection will shut off the affected FET. Likewise, if any cell voltage drops to a potentially damaging voltage level, the ATmega406 will automatically prevent further battery discharge by shutting down the discharge FET and going to a power-off mode.

With 40KB of flash program memory, 512 bytes of EEPROM for data parameter storage and 2KB of internal SRAM for program data, this new product packs the algorithm processing power necessary to implement battery monitoring and management for a full 4-cell laptop PC battery pack configuration. The device also includes the SM-bus interface for communication with the host application, and Atmel's self-programming Flash allows battery firmware upgrading through this or any other interface.

All parts of the ATmega406 are designed for low power consumption, drawing less than 1.2mA in active mode and less than 2?A in power-off mode.

A full suite of development tools supports ATmega406, including the JTAGICE mkII emulator and a smart battery development kit. The ATmega406 is housed in a 48-pin LQFP package, with pricing starting at $2.75 for volumes above 100,000.

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