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Maxim > Design Support > Technical Documents > Application Notes > Microcontrollers > APP 78
Keywords: high-speed microcontrollers, DS5230, DS5250, DS87C520, DS87C530, DS89C430, DS89C450,
power management, power consumption, battery-powered, stop mode, idle mode, pmm, crystal oscillator,
band-gap reference, ring oscillator, power control bit, PCON
APPLICATION NOTE 78
Using Power Management with High-Speed
Microcontrollers
By: Kevin Self
Mar 29, 2001
Abstract:
Power consumption
in battery-backed systems employing microcontrollers is discussed in this
application note. Most Maxim high-speed microcontrollers, including the DS87C520, DS89C450, DS80C400
and DS5250 utilize various methods of power management. This application note explores methods of power
management such as stop mode, idle mode, optimal clock frequency and external peripherals, to name a few.
Sample code is included to highlight new features specifically designed into these microcontrollers to minimize
power consumption.
Overview
Power management is critical in battery-powered applications. Differences of microamperes can translate into
months or years of operating life, which can make or break a product in the marketplace. The high level of
integration of Maxim microcontrollers makes them ideal for portable or battery-operated applications that
demand low power consumption. By combining the processor and peripherals onto a single die, redundant
hardware is eliminated, and power savings are achieved. In addition, power management features designed
into the High-Speed Microcontroller family further reduce power consumption.
The single largest factor in power consumption of a microcontroller is clock frequency. The power consumed
by a microprocessor is directly proportional to its operating speed, so it follows that a device operating at the
lowest possible frequency will produce the maximum power savings. The speed chosen depends on the
system requirements, most notably interrupt service time. Temperature can also affect power consumption.
Semiconductor devices draw greater power at lower temperatures. If the system under development is being
designed for cold temperatures, the designer should expect higher than typical power consumption values.
System design also has a direct bearing on power consumption, and driving large external loads will increase
power consumption.
This application note covers most members of the High-Speed Microcontroller family. Their power
management features are explained, and techniques are presented for minimizing power consumption.
Because the power management feature operates in conjunction with many of the peripheral functions,
especially the interrupt and serial functions, the user is urged to become familiar with the overall operation of
the processor before beginning this section. The software examples accompanying this application note can
be downloaded.
All the new power-management features reduce power consumption without sacrificing throughput or
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