In my previous blogs (see list below) I examined an MCU design's
active and standby modes, giving some suggestions to reduce the
current consumption. This installment is dedicated to the
transitions between active and standby modes. In applications
that demand deep sleep modes to maximize every nA, the
microcontroller should stay in sleep mode as long as possible.
It should also wake up to execute the next periodic task in the
shortest possible time and, when finished, return rapidly to
standby mode. Modern microcontrollers can be placed in a variety
of low-power modes, each corresponding to different values of
current consumption and different wakeup possibilities. This
variety provides product designers with a choice of sleep modes,
offering the flexibility to scale basic resources, and thereby
the power consumption, in several defined levels or energy
modes. But thereís little point in offering a microcontroller
with tremendous low sleep-mode energy consumption if its energy
efficiency gains are lost due t