RT8549L datasheet(13/24 Pages) RICHTEK

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RT8549L

DS8549L-00 May 2019

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Application Information

The RT8549L is a general purpose 4-CH LED driver and is

capable of delivering a maximum 180mA LED current. The

IC is a current-mode Boost converter integrated with a

60V/3.3A power switch and can cover a wide VIN range

from 4.2V to 24V. The part integrates both built-in soft-

start and with PWM dimming control; moreover, it provides

over voltage, over-temperature and current limit protections.

It also integrates PWM and mixed mode dimming function

for accurate LED current control. The PWM dimming

frequency can operate form 200Hz to 1kHz without

inducing any inrush current in LED and inductor.

Dimming Control

The RT8549L provides three dimming modes for controlling

the LED brightness. The three dimming modes include

PWM mode, DC mode and Mixed mode, and the dimming

mode could be set by register 00h. If the 00h[1:0] is set

11, the dimming mode is still in Mixed mode which is

shown in Table 2 below.

Address

Bit

Name

Default Value

Description

R/W

00 : PWM mode

01 : DC mode

00h

[1:0]

Dimming mode selection

DC mode (01)

10 : Mixed mode

R/W

Table 2. Dimming Control Mode Selection

PWM Mode

The ON/OFF of the current source is synchronized to the

PWM signal. The frequency of LED current is equal to

the PWM input signal.

DC Mode

The PWM signal will be monitored and calculate its duty.

The magnitude of ILED will be proportional to the duty.

ILED = IMAX x duty

Mixed Mode

When 25%

≤ PWM duty ≤ 100%, the PWM duty

modulated the amplitude of the current. (same as DC mode)

PWM duty < 25%, the DC dimming will translate to PWM

dimming, controlling the PWM duty instead by amplitude.

Slave Address : b0110001

Address

bit7

bit6

bit5

bit4

bit3

bit2

bit1

bit0

Default

Value

0x00

OVP

Reset [7]

OCP

Fault [4]

DIM_sig_

Sel [2]

Dimming Control [1:0]

0x01

OVP [6:5]

Current_

Limit [4]

Switching_frequency [3:0]

0x54

0x02

LED Current Setting [7:0]

0x00

0x03

Fault

Enable [7]

Fault Flag

Clear [3]

SLP [2]

SLP Latch

[1]

Fault Flag

[0]

0x80

0x04

SMBus Dimming Control [7:0]

0x00

0x06

Written

Check [7]

Vendor ID

0x80

Table 1. Register Map

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