A8504 데이터 시트보기 (PDF) - Allegro MicroSystems

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A8504

WLED/RGB Backlight Driver for Medium Size LCDs

Allegro MicroSystems 

A8504

WLED/RGB Backlight Driver for Medium Size LCDs

Features and Benefits

▪ Active current sharing between 6 LED strings for ±1.3%

typical current matching

▪ ±1.2% typical current accuracy

▪ Drive up to 11 series × 8 parallel = 88 LEDs

(Vf = 3.5 V, If = 40 mA)

▪ External PWM control for LED dimming

▪ An external resistor for LED current setting

▪ Boost converter with integrated 50 V, 2 A DMOS

▪ LED sinks rated for 45 mA

▪ 200 kHz to 2 MHz switching frequency

▪ Open LED disconnect

▪ Boost current limit, thermal shutdown, and soft start

▪ No audible ceramic capacitor noise during PWM dimming

▪ Adjustable overvoltage protection (OVP)

▪ No pull-up resistors required for LED modules that use

ESD capacitors

Package: 26 pin QFN/MLP (suffix EC)

Description

The A8504 is a multi-output WLED driver for medium display

backlighting. The A8504 integrates a boost converter and eight

current-sinks to provide a WLED/RGB backlight driver. The

boost converter can provide output voltage up to 47 V. The

flexible channel selection control and high voltage capability

allow a wide range of LED backlight applications. The boost

converter is a constant frequency current-mode converter. Each

LED channel can sink 45 mA, and channels can be paralleled

for higher currents. LED current can be controlled with external

PWM duty cycle.

The A8504 is available in a 26 pin, 4 mm × 4 mm QFN/MLP

package that is only 0.75 mm nominal in height. Applications

include:

▪ Thin notebook displays

▪ LCD TV

▪ RGB backlight

▪ GPS systems

▪ Portable DVD players

Approximate Scale 1:1

PWM pin dimming:

digital PWM input

VPWM

IOUT

CC

Typical Application

VIN

5 V ±10%

CIN

0.1 μF/ 10 V

VBAT

5 to 24 V

L1

10 μH

CBAT

2.2 μF/ 50 V

D1

ROVP

VOUT

COUT

VIN

SW SW OVP

PWM

SKIP

RFSET

COMP

FSET

ISET

RISET

LED1

LED3 LED5 LED7

A8504

LGND

GND

AGND

PGND

SEL3

SEL2

SEL1

LED2

LED8 LED6 LED4

2.2 μF

50 V

VIN

Figure 1. LCD monitor backlight, driving 11 green, blue, or white LEDs with Vf= 3.5 V, or 18 red LEDs with Vf = 2.2 V,

per LED string. Overvoltage protection set to 45 V nominal (40.5 V minimum). See also: Recommended Components

table, page 16.

8504-DS, Rev. 1

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