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ARM7-based MCUs integrate power-saving techniques

Posted: 04 Mar 2008 ?? ?Print Version ?Bookmark and Share

Keywords:ARM7 MCU? flash memory? power switches?

Atmel Corp. has announced a new series of high-performance, ultralow-power ARM7TDMI-based MCUs. The AT91SAM7L devices have embedded power switches controlling multiple power islands and programmable voltage regulators to reduce power consumption in active and standby modes.

The new product series features innovative power reduction techniques for both active and standby modes. In active mode, the power consumption is optimized via a programmable operating voltage, operating frequency and peripheral clock activity, and the use of DMA instead of the CPU for data transfers. The SAM7L operates in single supply mode down to 1.8V and consumes 0.5mA/MHz typical in active mode when executing code out of its flash memory. The power consumption in different standby modes is controlled via power switches, scalable voltage regulators and the use of sampling techniques on voltage monitors, power on reset and brown out detector instead of continuous measurement. This provides a high level of granularity while achieving power savings. In power down mode, the AT91SAM7L consumes a typical 100nA, which is believed to be a unique feature for 32bit MCUs.

In power-down mode, only the fast wake-up pin is supplied, allowing a system wake-up through a simple push button. This feature can be used to control power on/off in applications such as calculators. In backup mode, only the supply controller, the zero-power POR and the 32kHz oscillator remain running. The RTC, the 2K backup SRAM, the BOD, the charge pump, the LCD voltage regulator and the LCD Controller can be set on or off separately. This mode can be used when time, context or display need to be saved even if the main application is not running. In wait mode, the 2MHz RC oscillator provides a rapid wake-up time for fast external event management.

The AT91SAM7L128/64 embeds LCD features, including a segment LCD Controller, built-in drivers and the programmable LCD power supply for contrast control comprising a regulated charge pump and an adjustable voltage regulator. It is intended for monochrome passive LCD with up to 10 common terminals and up to 40 segment terminals.

The AT91SAM7L series has two members, the AT91SAM7L128 and the AT91SAM7L64, with 128Kbytes and 64Kbytes of flash memory, respectively. The AT91SAM7L series also integrates a wide range of peripheral functions, including USART, SPI, timer counter, RTC and ADCs. The AT91SAM7L128/64 system controller includes a reset controller capable of managing the power-on sequence. Correct device operation can be monitored by a built-in brown out detector and a watchdog timer running off an integrated oscillator. This complete set of system functions minimizes the number of external components as the chip can run at maximum speed without any external oscillator.

The SAM7L is supplied with a low-cost Starter Kit, the AT91SAM7L-STK, and runs the comprehensive set of application development tools that has been built up over the years for Atmel's ARM-based MCUs.

The AT91SAM7L128 and the AT91SAM7L64 are already available, packaged in a 128-pin LQFP package and a 144-pin 10mm x10mm 0.8mm ball pitch BGA package. Pricing is below $4 in volumes of 10,000 units.

Atmel is one of the exhibitors at the 13th IIC-China 2008.

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