Analog Devices ADM8832 a Datasheet

Charge Pump Regulator

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

for Color TFT Panel

ADM8832

FUNCTIONAL BLOCK DIAGRAM

C5

CC

TRIPLER

DISCHARGE

GND

2.2µF

VOLTAGE
DOUBLER

VOLTAGE

REGULATOR

DOUBLE

INVERTER

Figure 1.

LDO

TRIPLE

VOLTAGE

C1+
C1–
VOUT
LDO IN

+5VOUT
+5VIN

C2+
C2–
C3+
C3–

+15VOUT
C4+

C4–

–10VOUT

C2
1µF

C3
1µF

C4
1µF

C1

2.2µF

C6

2.2µF

+5.1V

C7

2.2µF

+15.3V
C8
1µF

–10.2V
C9
1µF

V

ADM8832

OFF

SHDN

OSCILLATOR

CONTROL

LOGIC

TIMING

GENERATOR

SHUTDOWN

CONTROL

VOLTAGE

CLKIN

SCAN/

BLANK

LDO_ON/

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 scan­ning 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).

03759-A-001

Rev. A

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.
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.

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Tel: [phone] www.analog.com
Fax: [phone] © 2004 Analog Devices, Inc. All rights reserved.

ADM8832

TABLE OF CONTENTS

Specifications..................................................................................... 3

Theory of Operation ...................................................................... 10

Timing Specifications .................................................................. 4

Absolute Maximum Ratings............................................................ 5

Thermal Characteristics .............................................................. 5

ESD Caution.................................................................................. 5

Pin Configuration and Function Descriptions............................. 6

Typical Performance Characteristics ............................................. 7

REVISION HISTORY

4/04—Changed from Rev. 0 to Rev. A

Changes to Outline Dimensions................................................... 11

Updated Ordering Guide............................................................... 11

7/03—Revision 0: Initial Version

Scanning and Blanking.............................................................. 10

Power Sequencing...................................................................... 10

Transient Response .................................................................... 10

External Clock ............................................................................ 10

Outline Dimensions....................................................................... 11

Ordering Guide .......................................................................... 11

Rev. A | Page 2 of 12

ADM8832

SPECIFICATIONS

VCC = 2.6 V to 3.6 V, TA = −40°C to +85°C, unless otherwise noted; C1, C5, C6, C7 = 2.2 µF, C2, C3, C4, C8, C9 = 1 µF, CLKIN = 1 kHz in
blanking mode.

Table 1.

Parameter Min Typ Max Unit Test Conditions

INPUT VOLTAGE, VCC 2.6 3.6 V
SUPPLY CURRENT, ICC 150 400 µA Unloaded, Scanning Period
70 140 µA Unloaded, Blanking Period
1 µA Shutdown Mode, TA = 25°C
+5.1 V OUTPUT

Output Voltage 5.0 5.1 5.2 V IL = 10 µA to 8 mA
Output Current 4 5 mA Scanning Period
5 8 mA Scanning Period, VCC > 2.7 V
50 200 µA Blanking Period
Power Efficiency 80 % VCC = 3 V, IL = 5 mA (Scanning)
70 % VCC = 3 V, IL = 200 µA (Blanking)
Output Ripple 10 mV p-p 8 mA Load
Transient Response 5 µs IL Stepped from 10 µA to 8 mA

+15.3 V OUTPUT

Output Voltage 14.4 15.3 15.6 V IL = 1 µA to 100 µA
Output Current 50 100 µA Scanning Period
1 10 µA Blanking Period
Output Ripple 50 mV p-p IL = 100 µA

−10.2 V OUTPUT
Output Voltage −10.4 −10.2 −9.6 V IL = –1 µA to −100 µA
Output Current −100 −50 µA Scanning Period

−10 −1 µA Blanking Period
Output Ripple 50 mV p-p IL = –100 µA

POWER EFFICIENCY 90 % Relative to 5.1 V Output, IL = 100 µA (Scanning)
(+15.3 V and −10.2 V Outputs) 80 % Relative to 5.1 V Output, IL = 10 µA (Blanking)
CHARGE PUMP FREQUENCY 60 100 140 kHz Scanning Period
CONTROL PINS

SHDN

Input Voltage, V

0.7 VCC V
Digital Input Current ±1 µA
Digital Input Capacitance1 10 pF

SCAN/BLANK

Input Voltage 0.3 VCC V

0.7 VCC V High = SCAN Period
Digital Input Current ±1 µA
Digital Input Capacitance1 10 pF

LDO_ON/OFF

Input Voltage 0.3 VCC V Low = External LDO

0.7 VCC V High = Internal LDO
Digital Input Current ±1 µA
Digital Input Capacitance1 10 pF

Footnotes after table.

0.3 VCC V

SHDN

Low = Shutdown Mode

SHDN

High = Normal Mode

SHDN

Low = BLANK

Period

Rev. A | Page 3 of 12

ADM8832

Parameter Min Typ Max Unit Test Conditions

CLKIN

Minimum Frequency 0.9 1 kHz Duty Cycle = 50%, Rise/Fall Times = 20 ns
Input Voltage

VIL 0.3 VCC V
VIH 0.7 VCC V

Digital Input Current ±1 µA
Digital Input Capacitance1 10 pF

1

Guaranteed by design. Not 100% production tested.

Specifications are subject to change without notice.

TIMING SPECIFICATIONS

VCC = 2.6 V to 3.6 V, TA = –40°C to +85°C, unless otherwise noted; C1, C5, C6, C7 = 2.2 µF, C2, C3, C4, C8, C9 = 1 µF, CLKIN = 1 kHz in
blanking mode.

Table 2.

Parameter Min Typ Max Unit Test Conditions/Comments

POWER-UP SEQUENCE

+5 V Rise Time, t
+15 V Rise Time, t

−10 V Fall Time, t
Delay between −10 V Fall and +15 V, t

POWER-DOWN SEQUENCE

+5 V Fall Time, t
+15 V Fall Time, t

−10 V Rise Time, t

300 µs 10% to 90%, Figure 17

R5V

8 ms 10% to 90%, Figure 17

R15V

12 ms 90% to 10%, Figure 17

F10V

3 ms Figure 17

DELAY

75 ms 90% to 10%, Figure 17

F5V

40 ms 90% to 10%, Figure 17

F15V

40 ms 10% to 90%, Figure 17

R10V

Rev. A | Page 4 of 12