Charge Pump Regulator

for Color TFT Panel

ADM8832

Rev. A

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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

FUNCTIONAL BLOCK DIAGRAM

LDO

VOLTAGE

REGULATOR

VOLTAGE

DOUBLER

DISCHARGE

C1+

C1–

VOUT

LDO IN

+5VOUT

+5VIN

C2+

C2–

C3+

C3–

+15VOUT

C4+

C4–

–10VOUT

C1

2.2

µF

C6

2.2

µF

C2

1

µF

C7

2.2

µF

+5.1V

C3

1

µF

+15.3V

C8

1

µF

C4

1

µF

–10.2V

C9

1

µF

VOLTAGE

TRIPLER

DOUBLE

TRIPLE

VOLTAGE

INVERTER

CLKIN

SCAN/

BLANK

LDO_ON/

OFF

GND

TIMING

GENERATOR

CONTROL

LOGIC

SHUTDOWN

CONTROL

OSCILLATOR

ADM8832

C5

2.2

µF

SHDN

Figure 1.

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

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).