TABLE OF CONTENTS Power management needs have proliferated exponentially with the variety of mobile phones, and device features and functions. As long as the mobile phone was simply required to make and receive phone calls, it embodied one set of power management requirements. However, as mobile phone manufacturers have heaped on the features, each requirement has placed another demand on power management.
Raising the data rate for mobile phones and adding an Internet browser put extra demands on battery life. Color liquid crystal display (LCD) screens with white LED backlighting taxes battery life, as does the complementary metal-oxide-semiconductor (CMOS) image sensors used to take pictures for camera phones. New embodiments of the camera phone compete with digital still cameras, with mega pixel sensors, auto focus motors, and high-intensity white LED flash attachments. The same portable device may include an MPEG-4 codec for video and an MP3 audio player, with built-in piezo-electric speakers and surround-sound decoders.
In addition to this, the mobile phone must also work in different areas of the world. It must include multiple radio transmitters to respond to different standards. To enable communication between PC databases and hands-free headsets, the mobile device will include Bluetooth and 802.11 Wireless LAN attachments.
Power management would be much simpler if all portable electronics required the same operating voltage. But typical mobile devices use a number of voltages. For example, one voltage is required to power the mobile device's central processor, one for the core, another for the I/O sections, and one for the...
