Editor's Note: View the Fundamentals of Microcontrollers to catch up on the architectural differences, selection, set up and programming of today's micros.
For a system designer looking to choose a microcontroller, the vast array of available MCUs can make the search quite complex. Silicon Labs has announced an 8-bit microcontroller with a core voltage of 0.9 volt. Texas Instruments makes many low-power claims with the 16-bit MSP430. Infineon and Freescale have many automotive microcontrollers to go along with their extensive nonautomotive MCU lineups. Atmel's AVR and Microchip's PIC families keep adding variations. New 32-bit ARM Cortex-M3 devices are constantly being announced, while the 8-bit 8051 core still forms the basis of many diverse microcontrollers. And market leader Renesas has something for everyone.
To work through the thicket of choices, it's helpful to assess current trends in the industry. How are microcontrollers changing? What will future microcontrollers look like? Perhaps most crucial from the designer's point of view are the trends toward lower power and greater integration.
Power is on the minds of the microcontroller vendors today, and with good reason. Many applications now run on batteries, in situations where the system power consumption is directly related to the run-time, or life of the system. Also, as the world grapples with rising energy prices and global warming, even applications that are plugged into the wall need to reduce the juice.
There are two types of power dissipation figures to watch for: dynamic and static power. Dynamic, or operating, power addresses the power consumed during a typical application. This is where the general efficiencies of the microcontroller architecture come into play. Static power (also called standby or leakage power) represents the power the device consumes when in standby or other low-power mode. This is critical for many battery-powered applications, especially those waiting for an external event before any processing takes place.
Die photograph of a 1980 Intel 8051 microcontroller
A microcontroller may have many low-power modes, depending on the application. There are numerous methods that the microcontroller can use to lower the static power, including low-leakage transistors and turning off the power to various parts of the MCU. Usually, the deeper "asleep" the device is, the longer the it takes to wake up. Wakeup time is an important consideration when determining how just low you can go with low-power modes.
Some vendors have pushed down the supply voltage of their processor cores to lower one part of the power equation. This helps, particularly for dynamic operation; but current levels, naturally, still need to be considered.
Increased silicon integration
In this age of systems-on-chip and advances in semiconductor process technology, it is easier to implement more mixed-signal peripherals onto the microcontroller die. Many vendors now offer a tremendous amount of flexibility in the types and sizes of memory, and all manner of peripheral options.