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ADM8832ACP-REEL7

Charge Pump Regulator for Color TFT Panel

Analog Devices 

FEATURES

3 output voltages (+5.1 V, +15.3 V, −10.2 V) from one 3 V

input supply

Power efficiency optimized for use with TFT in mobile

phones

Low quiescent current

Low shutdown current (<1 µA)

Fast transient response

Shutdown function

Power saving during blanking period

Option to use external ldo

APPLICATIONS

Handheld instruments

TFT LCD panels

Cellular phones

GENERAL DESCRIPTION

The ADM8832 is a charge pump regulator used for color thin

film transistor (TFT) liquid crystal displays (LCD). Using charge

pump technology, the device can be used to generate three

output voltages (+5.1 V ±2%, +15.3 V, −10.2 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 −10.2 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 −10.2 V

outputs if so required by the user.

The ADM8832 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

Charge Pump Regulator

for Color TFT Panel

ADM8832

FUNCTIONAL BLOCK DIAGRAM

CLKIN

SCAN/

BLANK

LDO_ON/

OFF

SHDN

VCC

ADM8832

C5

2.2µF

VOLTAGE

DOUBLER

OSCILLATOR

CONTROL

LOGIC

LDO

VOLTAGE

REGULATOR

DOUBLE

TIMING

GENERATOR

TRIPLE

VOLTAGE

TRIPLER

VOLTAGE

SHUTDOWN DISCHARGE INVERTER

CONTROL

GND

Figure 1.

C1+

C1–

VOUT

LDO IN

+5VOUT

+5VIN

C2+

C2

C2– 1µF

C3+

C3

C3– 1µF

+15VOUT

C4+

C4

C4– 1µF

–10VOUT

C1

2.2µF

C6

2.2µF

+5.1V

C7

2.2µF

+15.3V

C8

1µF

–10.2V

C9

1µF

mode where the current is highest. During blanking periods, the

ADM8832 switches to 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 seamlessly maintained when switching from scan-

ning mode to blanking mode or vice versa.

The ADM8832 power saving features include low power

shutdown and reduced quiescent current consumption during

the blanking periods. 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™). 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 ADM8832 is fabricated using CMOS technology for minimal

power consumption. The part is packaged in a 20-lead LFCSP

(lead frame chip scale package).

Rev. A

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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.

Specifications subject to change without notice. No license is granted by implication

or otherwise under any patent or patent rights of Analog Devices. Trademarks and

registered trademarks are the property of their respective owners.

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781.329.4700

www.analog.com

Fax: 781.326.8703 © 2004 Analog Devices, Inc. All rights reserved.

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