Energy efficiency is a key
design consideration in a
National Semiconductor line
of ICs intended for batterypowered
phone and video systems.
Minimizing power consumption
is the common thread in these
circuits, which convert digital data into
real-world video playback subsystems
(see the figure). This involves efficient
power sources plus digital techniques that
minimize power dissipation using analog,
digital, and mixed-signal technology ICs.
Application processors for video systems
consume substantial energy, which
limits battery life. To minimize these
requirements, National’s PowerWise
technology uses adaptive voltage scaling
(AVS). Integrated onto these processors
along with compatible power-management
ICs like the LP5552, AVS reduces
energy consumption by up to 70%,
extending battery life.
With AVS, these processors can adaptively
adjust its supply voltage to the minimum
level needed, greatly reducing its
energy consumption. The LP5552
includes two 800-mA buck regulators
and five low-dropout regulators (LDOs).
For powering baseband functions,
there’s the LP3919 power-management
IC, which features high-efficiency switching
regulators, LDOs, and a battery
charger. It powers the baseband processor
as well as other system circuitry.
ENHANCING THE DISPLAY
National’s low-power Mobile Pixel Link
(MPL) family streams large quantities of
data (seen as video and graphic images)
to an LCD while maximizing battery life.
The MPL device serializes the data to
reduce the wire count, which decreases
the size of the connector and flexible pc
board. MPL reduces electromagnetic
interference (EMI), and its power consumption
is roughly half that of similar
products. In addition, MPL handles the
voltage-level translation between the
host and the display, eliminating the need
for an external level shifter.
The newest MPL, the highspeed
LM2512 serial host
device, supports a video-mode
interface bridge between the
processor and the display. It’s
highly programmable, with a
built-in lookup table that
allows color correction, so
designers can optimize
video viewing. The
LM2512 also includes
a dithering function,
allowing 24-bit video
to be displayed with
high quality on 18-bit
displays, preserving the
lower power consumption
associated with 6-
bit RGB (red-greenblue)
data converters.
The FPD95120, a
highly integrated, high-performance,
low-temperature
polycrystalline silicon
(LTPS) display
driver, is the narrowest
glass-mounted device available for half-
VGA format. Its 0.9-mm width maximizes
display glass active area. Also, it
provides an MPL deserializer, a high-efficiency
inductive dc-dc switcher, and
RAM to enable standby, low-power display
capabilities.
BACKLIGHTING AND COLOR
Compared to white LEDs, RGB LED
drivers provide better colors on the display
and lower power consumption. The
LP5520 offers a small and simple solution
without the need for optical feedback,
producing a true white light over a
wide temperature range while improving
the color gamut from 70% up to 100%
of the NTSC standard. In the adaptive
mode, driver circuitry automatically
adjusts the output voltage for the lowest
possible power consumption.
The LP5521, LP5522, and LP55281
color-management chips feature lowpower
color LED drivers for handheld
lighting applications. The digital core
processes data received from nonvolatile
storage, such as a secure digital
card, flash, or a micro hard drive.
Each of these sources presents a
unique energy-consumption challenge
in handheld devices.
To power a micro hard drive, the
LM3668 buck-boost regulator provides
a 3.3-V output voltage to power the
driver motor. It offers greater than 90%
efficiency in buck and boost modes,
which is essential for driving high-power
applications. The lithium-ion battery
in handheld devices discharges from levels
above 3.3 V to below 3.3 V.
Sending data wirelessly consumes significant
battery power. The LM3207 dcdc
power supply, optimized for 3G RF
power amplifiers, dynamically reduces
the power amplifier’s energy consumption
by tightly regulating the RF power
amplifier supply voltage to the lowest
possible level while maintaining poweramplifier
linearity.