LT1947| Datasheet

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LT1947 Adjustable Output TFT-LCD Triple Switching Regulator
FEATURES

DESCRIPTIO

Complete Solution Under 1.2mm Develops Three Outputs from a 3.3V or 5V Supply Externally Programmable VON Delay Fixed Frequency Low Noise Outputs All Ceramic Capacitors 3MHz Switching Frequency Fast Transient Response Few External Components Required 2.7V to 8V Input Range Adjustable AVDD and VON Voltages Tiny 10-Lead MSOP and Thermally Enhanced 10-Lead MSOP Packages

APPLICATIO S

TFT-LCD Notebook Display Panels TFT-LCD Desktop Monitor Display Panels Digital Cameras Handheld Computers

The LT 1947 is a highly integrated multiple output DC/DC converter designed for use in TFT-LCD panels. The device contains two independent switching regulators. The main regulator has an adjustable output voltage with an internal 1.1A switch that can generate a boosted voltage as high as 30V. The second regulator's output is also adjustable up to 30V and can deliver 10mA for positive bias. A simple level-shift charge pump off the main switch node generates the negative bias voltage. An external capacitor sets the delay time from AVDD's final value to the rising edge at the VON pin. The 3MHz switching frequency allows the use of tiny low profile chip inductors and capacitors throughout, providing a low noise, low cost total solution with all components under 1.2mm in height. The device operates from an input range of 2.7V to 8V and is available in 10-lead MSOP and thermally enhanced 10-lead MSOP packages.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

TYPICAL APPLICATIO

D3

D4

L1 3.3uH VIN L2 4.7uH C1 2.2uF CERAMIC

C6 0.68uF

D1 VIN SW2 SW1 FB1

C4 0.68uF CERAMIC AVDD 8V 200mA R1 53.6k C2 3.3uF CERAMIC 2
VSHDN 5V/DIV VON 20V/DIV

VOFF 8V 10mA

D2 VO2 C3 220nF R3 182k FB2 R4 10k SHDN CT C5 10nF D1: MBRM120LT3 D2: CMDSH-3 D3, D4: BAT54S DUAL DIODE L1: SUMIDA CLQ4D103R3 L2: TAIYO YUDEN LB2012B4R7M VON GND LT1947 R2 10k

VON 24V 10mA

AVDD 10V/DIV

SHUTDOWN

VOFF 10V/DIV
1947 F01

C1: TAIYO YUDEN LMK316BJ225MD C2: TAIYO YUDEN LMK325BJ335MD 2 C3: AVX 0.22uF 25V X7R C4, C6: TAIYO YUDEN LMK107BJ684MA

Figure 1. 3.3V Powered TFT-LCD Bias Generator
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Start-Up Waveforms
2ms/DIV
1947 TA01.tif

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LT1947 DATASHEET