AN2433 Freescale Semiconductor / Motorola, AN2433 Datasheet - Page 25

• Manufacturer Part Number: AN2433
• Description: 5V to 3V Design Considerations
• Manufacturer: Freescale Semiconductor / Motorola

Conclusions
MOTOROLA
This application note discusses the design considerations which should be
taken into account when moving a microcontroller application from today’s 5V
technology to tomorrow’s 3V technology.
The growing popularity for lower voltage systems forces components to be
designed and manufactured only for 3V operation, and this trend has also
reached the microcontroller market. The new generations of MCUs are now
moving to sub 0.25 micron processes and supply voltages of 3V or less.
The advantages of low voltage MCUs include:
Designers now moving from 5V to 3V technology will be required to create
systems in an interim period using a mixture of both 5V and 3V components.
During this transition time, components allowing the translation from 3V to 5V
and vice versa will be needed. Thus the migration to 3V technology brings also
challenges which need to be considered:
Interfacing 5V outputs peripherals to 3V MCU inputs via a level shifter typically
causes no issues, as the output voltage swing of 5V devices is sufficient to
reliably drive 3V inputs.
Interfacing 3V MCU outputs to 5V TTL peripheral inputs does not constitute a
problematic task, as 3V CMOS outputs have enough margin to drive 5V TTL
inputs (voltage-translation devices come into place to facilitate interfacing).
Interfacing 3V MCU outputs to 5V CMOS peripheral inputs is more demanding,
but careful design of level shifters using discrete or specially designed interface
devices will address these situations.
The 5V to 3V technology move opens a challenging scenario for systems
designers. This report shows the benefits that will accrue from such a change
and also identifies topics that require further investigation in order to make this
transition as smooth as possible.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Ability to reduce power consumption
Smaller on board power sources
Increase in operational lives of battery powered applications
Decrease in battery weight of portable applications
Lower costs for the overall system
5V to 3V Design Considerations
Go to: www.freescale.com
Conclusions
AN2433/D
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