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7903A – AVR – 2006/02

Ultra Low Power Memory

There is often a trade-off between power consumption and robustness, accuracy, speed

and fast start-up time in analog modules. The analog modules therefore require other

methods differing from the digital designs to maintain good performance and still achieve

low power consumption. AVR MCUs feature high-quality analog modules with more current

consumption, but turns them off whenever they are not in use. This approach minimizes

current consumption without sacrificing accuracy or performance.

Flash Memory Power Consumption and Flash Sampling

Flash memory is an analog bloc with a static current consumption. Traditional Flash

memory designs are always enabled while in active mode. However, at low clock

frequencies the Flash read time is less than the clock period so it can be disabled to

significantly reduced power consumption. When the clock is running at a few MHz or less,

AVR controllers use a technique called “Flash sampling” that enables the Flash for only

about 10 nanoseconds to sample the array’s contents and then immediately disables it

thereby, reducing average power consumption. (Figure 6).

Figure 6: Flash sampling system

Figure 7: Flash Sampling vs Flash Always On

The Flash sampling technique enables a robust, low power Flash design that operates

from 1.8 to 5.5V.