ADM8832

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 A)
Fast transient response
Shutdown function
Power saving during blanking period
Option to use external ldo


Application

Handheld instruments
TFT LCD panels
Cellular phones


Pinout




Specifications

Supply Voltage                                                                      −0.3 V to +4.0 V
Input Voltage to Digital Inputs                                              −0.3 V to +4.0 V
Output Short Circuit Duration to GND                                    10 sec
Output Voltage
        +5.1 V Output                                                                −0.3 V to +6 V
        −10.2 V Output                                                              −12 V to +0.3 V
        +15.3 V Output                                                              −0.3 V to +17 V
Operating Temperature Range                                              −40°C to +85°C
Power Dissipation (Derate 33 mW/°C above 25°C)              3.55 W
Storage Temperature Range                                                 −65°C to +150°C
ESD                                                                                       Class I


Description

The ADM8832 is a charge pump regulator used for color thin film transistor (TFT) liquid crystal displays (LCD). Using charge pump technology, ADM8832 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 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).