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GENERAL DESCRIPTION
鈥?0VOUT
GND
The ADM8830 is a charge pump regulator used for color thin
film transistor (TFT) liquid crystal displays (LCDs). Using
charge pump technology, the device can be used to generate three
output voltages (+5.1 V 卤 2%, +15.3 V, 鈥?0.2 V) from a single
3 V input supply. These outputs are then used to provide
supplies for the LCD controller (5.1 V) and the gate drives for
the transistors in the panel (+15.3 V and 鈥?0.2 V). Only a few
external capacitors are needed for the charge pumps. An efficient
low dropout voltage regulator also ensures that the power
efficiency is high and provides a low ripple 5.1 V output. This
LDO can be shut down and an external LDO used to regulate
the 5 V doubler output and drive the input to the charge pump
section, which generates the +15.3 V and 鈥?0.2 V outputs if so
required by the user.
The ADM8830 has an internal 100 kHz oscillator for use in
scanning mode, but the part must be clocked by an external clock
source in blanking (low current) mode. The internal oscillator is
used to clock the charge pumps during scanning mode where the
current is highest. During blanking periods, the ADM8830
switches to use an external, lower frequency clock. This allows the
user to vary the frequency and maximize power efficiency during
blanking periods. The tolerances on the output voltages are
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seamlessly maintained when switching from scanning mode to
blanking mode or vice versa.
The ADM8830 has a number of power saving features, including
low power shutdown and reduced quiescent current consumption
during the blanking periods mentioned above. The 5.1 V output
consumes the most power, so power efficiency is also maximized
on this output with an oscillator enabling scheme (Green Idle鈩?.
This effectively senses the load current that is flowing and turns
on the charge pump only when charge needs to be delivered to
the 5 V pump doubler output.
The ADM8830 is fabricated using CMOS technology for minimal
power consumption. The part is packaged in 20-lead LFCSP
and TSSOP packages.
REV. B
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
that may result from its use. No license is granted by implication or oth-
erwise under any patent or patent rights of Analog Devices. Trademarks
and registered trademarks are the property of their respective owners.
One Technology Way, P Box 9106, Norwood, MA 02062-9106, U.S.A.
.O.
Tel: 781/329-4700
www.analog.com
Fax: 781/326-8703
漏 2003 Analog Devices, Inc. All rights reserved.
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