AN2433 Freescale Semiconductor / Motorola, AN2433 Datasheet - Page 2

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

AN2433/D
Introduction
Low Voltage Microcontrollers
2
Hand-held and mobile communication products continue to require longer
battery life and/or smaller product sizes. Both features are made possible by
low voltage microcontrollers (MCUs) that help to reduce system power
consumption, which then decreases system costs.
While moving to more energy efficient products, designers may need to use a
mixture of both 5V and 3V components due the to lack of availability of all the
necessary 3V components
challenging scenario for system designers. This application note will address
the benefits that such a change brings and the design considerations that make
the transition as smooth as possible.
The market demand for low-voltage systems is gradually increasing due to the
requirements for lower power consumption. The technology itself is also a
strong driving force towards this change, with semiconductor companies
reducing the geometry of the internal circuitry of the new generation of
components in order to remain competitive. With smaller geometries, it is
possible to integrate more circuits closer together and offer increasing
functionality in the same area of silicon.
The new generation of MCUs is now moving below 0.25 µm processes. As
transistor oxide thickness and channel lengths decrease, lower operating
voltages are essential to avoid over stressing the transistor and causing
reliability concerns such as gate oxide breakdown, punch-through and hot-
electron effects.
Semiconductor manufacturers continually make steps in designing more and
more products capable of operating at 3V (or less). This will soon eliminate the
necessity of having additional interfacing devices that increase the power
dissipation, complexity, size and cost of an application.
1.
5.5V) to 3.3V systems with V
and 3V are used in different parts of the analysis, dependent on the supply voltage tolerance of the logic
family in question. The main points of the analysis remain unaffected.
In the following discussion we will assume interfacing between 5V systems with V
Freescale Semiconductor, Inc.
For More Information On This Product,
5V to 3V Design Considerations
Go to: www.freescale.com
DD3
= 3.3V ±10% (3.0 – 3.6V) and vice-versa. The reader will notice that 3.3V
1
. The move from 5V to 3V technology creates a
DD5
= 5V ±10% (4.5 –
MOTOROLA