Rainbow-electronics MAX17127 Manual do Utilizador descarregar pdf

_______________________________________________________________ Maxim Integrated Products 1

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

MAX17127

Six-String WLED Driver with Integrated

Step-Up Converter

General Description

The MAX17127 is a high-efficiency driver for white light-

emitting diodes (LEDs). It is designed for large liquid-

crystal displays (LCDs) that employ an array of LEDs as

the light source. An internal switch current-mode step-up

converter drives the LED array, which can be configured

for up to six strings in parallel and 13 LEDs per string.

Each string is terminated with ballast that achieves Q2%

current-regulation accuracy, ensuring even LED bright-

ness. The MAX17127 has a wide input voltage range

from 5V to 26V, and provides adjustable 10mA to 30mA

full-scale LED current.

The MAX17127 can implement brightness control through

the PWM signal input, and LED current is directly con-

trolled by the external dimming signal’s frequency and

duty cycle.

The MAX17127 has multiple features to protect the con-

troller from fault conditions. Once an open/short string is

detected, the fault string is disabled while other strings

can still operate normally. The controller features cycle-

by-cycle current limit to provide constant operation and

soft-start capability. If the MAX17127 is in current-limit

condition, the step-up converter is latched off after an

internal timer expires. A thermal-shutdown circuit pro-

vides another level of protection. When thermal shut-

down happens, the MAX17127 is latched off.

The MAX17127’s step-up controller features an inter-

nal 0.12I (typ), 48V (max) power MOSFET with local

current-sense amplifier for accurate cycle-by-cycle cur-

rent limit. This architecture greatly simplifies the external

circuitry and saves PCB space. Low-feedback volt-

age at each LED string helps reduce power loss and

improve efficiency. The MAX17127 features resistor-

adjustable switching frequency from 250kHz to 1MHz,

which enables a wide variety of applications that can

trade off component size for operating frequency.

The MAX17127 is available in a thermally enhanced,

lead-free, 20-pin, 4mm x 4mm thin QFN package.

Features

S 5V to 26V Input Supply Voltage

S Up to Six Parallel Strings Multiple Series-

Connected LEDs

S 250kHz to 1MHz Adjustable Switching Frequency

S 0.12I Internal HV Power MOSFET (48V max)

S Low String Feedback Voltage: 480mV at 20mA

LED Current

S Full-Scale LED Current Adjustable from 10mA to

30mA

S Q2% Current-Regulation Accuracy Between

Strings

S 400ns Minimum String On-Time

S 100Hz to 25kHz PWM Input Range

S Open and Short LED Protection

S Output Overvoltage Protection

S Thermal Shutdown

S Small 20-Pin, 4mm x 4mm Thin QFN Package

Applications

Notebook, Subnotebook, and Tablet Computer

Displays

Automotive Systems

Handy Terminals

19-5164; Rev 0; 3/10

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Simplified Operating Circuit appears at end of data sheet.

Ordering Information

EVALUATION KIT

AVAILABLE

PART TEMP RANGE PIN-PACKAGE

MAX17127ETP+ -40°C to +85°C 20 TQFN-EP*

1 2 3 4 5 6 ... 21 22

Resumo do Conteúdo

Página 1 - Step-Up Converter

_______________________________________________________________ Maxim Integrated Products 1For pricing, delivery, and ordering information, pleas

Página 2

10 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

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Página 4

12 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 5

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Página 6

14 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 7

______________________________________________________________________________________ 15MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 8 - = 12V, T

16 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 9 - TOP VIEW

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Página 10

18 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 11 - Table 1. Component List

______________________________________________________________________________________ 19MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 12 - Table 2. Component Suppliers

2 ______________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 13

20 _____________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 14 - Frequency Selection

______________________________________________________________________________________ 21MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 15 - Table 3. FPO Function Table

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

Página 16 - Thermal Shutdown

_______________________________________________________________________________________ 3MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 17 - Inductor Selection

4 ______________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 18 - Output Capacitor Selection

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Página 19 - LED Selection and Bias

6 ______________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 20 - PCB Layout Guidelines

_______________________________________________________________________________________ 7MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 21 - PROCESS: BiCMOS

8 ______________________________________________________________________________________MAX17127Six-String WLED Driver with Integrated Step-Up Co

Página 22

_______________________________________________________________________________________ 9MAX17127Six-String WLED Driver with Integrated Step-Up Co

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