RT4531 datasheet(3/14 Pages) RICHTEK

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RT4531

DS4531-01

July 2016

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Function Block Diagram

Operation

The RT4531 is a high efficiency solution with 10S2P string

for backlight applications. The RT4531 optimizes the

feedback regulation voltage to provide high efficiency and

also keep high current matching. The RT4531 can receive

either the 1-wire dimming at EN pin or PWM dimming at

PWM pin for brightness dimming. If the 1-wire dimming is

selected, the PWM pin should be kept high; If the PWM

dimming is selected, the EN pin should be kept high.

OCP Protection

The RT4531 features a 1.5A OCP. The driver provides

cycle-by-cycle current limit function to control the current

on power switch. The boost switch turns off when the

inductor current reaches this current threshold and it

remains off until the beginning of the next switching cycle.

This protects the RT4531 and external component under

overload conditions.

OTP Protection

The OTP function will disable boost and current source

when the junction temperature exceeds 150

°C. Then

restart to soft-start when the junction temperature is

smaller than 135

°C.

OVP Protection

The OVP function monitors the SW pin's voltage. Once it

exceeds OVP threshold = 36.5V twice, the boost and

current source will be latched off. Until PWM or EN go

high from low again, the latch state will be released.

1-wire Brightness Dimming

The RT4531 is built-in a 10-bit resolution brightness

control. The EN pin features a simple 1-wire interface to

allow digital brightness control. If the 1-wire dimming is

needed, signals of a specific pattern should be input

detection window into EN pin; Otherwise, PWM pin need

to be enabled.(refer to Timing Diagram1 for Continuous

Coding).The Register Program and register map give an

overview of the protocol used by RT4531.

PWM Brightness Dimming

Besides programmable built-in 1-wire backlight LED

current control, the RT4531 features a built-in PWM

dimming current control by PWM pin, offering a linear

current dimming by external clock source. In order to

guarantee the PWM dimming resolution, recommending

PWM dimming frequency have to be operated at range of

20kHz to 100kHz.

Control

Logic

Current Source/

FB Short Detect

IFB1

IFB2

PWM/Drv

GND

UVLO

VIN

OCP

OSC

MINFB

PWM

Logic

DC to DC Core

ISET

PWM

ISET

OVP

OTP

OVP

AGND

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