Linear Design Features LTMag-V18N03-10-LT3513 - Kevin Huang Owner's Manual Technical Guide

L DESIGN IDEAS

5-Output High Current Power Supply for TFT-LCDs in a Low Profile QFN Features Space-Saving 2MHz Switching Regulators by Kevin Huang

Introduction L1 DFLS240L 10µH

VIN VLOGIC

The LT3513 is a highly integrated, 8V TO 30V 5V

5-output regulator designed to pro- ZHCS400 0.47µF

VOFF Si2333DS vide all the supply voltages typically –10V

L2 UVLO LDOPWR VIN SW2

required by large TFT liquid crystal 2.2µF AVDD

10µH SW4 FB2

displays (LCDs) with a single IC. The 80m A

69.8k D4 PGOOD

part features a step-down switching NFB4 RUN-SS1

10k BIAS RUN-SS2

regulator to produce a 3.3V or 5V

BOOST RUN-SS3/4

logic voltage from a wide voltage range 0.22µF

4.7µH CT

VLOGIC SW1 47n F 15n F 15n F 15n F

input, such as automotive battery.

5V LT3513

SENSE+

A lower voltage logic supply can be 0.5A

30.1k VON_CLK VON_CLK

SENSE– VON

generated from the first supply by 22µF FB1 VON 22V

10k DFLS240L VONSINK

adding an external NPN driven by an

internal linear regulator. The other 165k

ZXTAM322 6.8µH

VLOGIC

BD SW3

three on-chip regulators provide the VLDO 5V

FB5 FB3 0.47µF

three bias voltages required by LCDs: a 0.5A

VC1 VC2 GND VC3 VC4

high power boost regulator to generate

AVDD, a low power boost regulator to 10k

generate VON and an inverting regula-

L1: SUMIDA CDR6D28MNNP-100NC L2: COILCRAFT LPO3310-103MLC

tor to provide VOFF.

L3: SUMIDA CDR6D28MNNP-4R5NC L4: COILCRAFT LPO3310-682MLC

Switching regulators are chosen

Figure 1. A complete 5-output 2MHz TFT-LCD power supply

over linear regulators to accommodate

a wide input voltage range (providing Operation

both step up and step down functions) All of the regulators are syn- Figure 1 shows a 5-output TFT LCD and to minimize power dissipation. chronized to a 2MHz internal clock, power supply that can accommodate The LT3513’s wide input range, 4.5V allowing the use of small, low cost an 8V to 30V input voltage. The first to 30V, allows it to accept a variety of inductors and ceramic capacitors. switching converter produces a 5V power sources, including automotive Since different types of panels may re- logic supply using a buck regulator. batteries, distributed supplies and quire different bias voltages, all output The internal linear regulator with an wall transformers. The low profile voltages are adjustable for maximum external NPN produces a 3.3V logic 38-pin QFN package has an exposed flexibility. Programmable soft-start supply using the 5V supply as input. metal pad on the backside to maximize capability is included in each of the The second switcher is used to boost thermal performance. regulators to limit inrush current. the 5V supply to an 8V, 80m A AVDD

5-Output High Current Power Supply

RUN/SS 2V/DIV

for TFT-LCDs in a Low Profile QFN VLOGIC 5V/DIV Features Space-Saving 2MHz AVDD 10V/DIV Switching Regulators ........................30 VOFF 10V/DIV Kevin Huang

32VIN Synchronous Buck Regulators with Integrated FETs Deliver up to 12A

from Sub-1mm Height Packages ........32 VE3 20V/DIV

Stephanie Dai and Theo Phillips

VON 20V/DIV IIN(AVG) 1A/DIV

Complete Power Solution for Digital Cameras and Other Complex Compact Portable Applications ........................34

5ms/DIV

Brian Shaffer

Figure 2. Startup waveforms of the power supply in Figure 1

Linear Technology Magazine • September 2008