RT8489 Datasheet, PDF (1/16 Pages) Richtek Technology Corporation – High Voltage 4-CH LED Driver Controller

®
RT8489
High Voltage 4-CH LED Driver Controller
General Description
The RT8489 is a 4-CH LED driver controller that delivers
well matched LED current to each channel of LED string.
With external current sources, the number of LEDs per
string is only limited by the current source and the V_IN/
V_OUT conditions. The current mode PWM Boost type
controller operates at an adjustable switching frequency
of up to 1MHz, with a wide V_IN range covering from 7V to
28V. The switch driver is designed to drive industrial grade
high power MOSFETs.
The PWM loop selects and regulates the LED string with
the highest voltage string to 0.7V, thus allowing voltage
mismatches between the LED strings. The RT8489
automatically detects and excludes any open and/or
broken strings during operation from the PWM loop to
prevent V_OUT from over voltage.
The LED currents on all channels are simply adjustable
with a resistor on each channel. Three convenient dimming
methods are provided : 1. Analog dimming is linearly
controlled by an external voltage. 2. True digitally
controlled PWM dimming can regulate the duty cycle of
the LED current. 3. For noise free PWM dimming, use an
on board output clamping amplifier as a low pass filter to
convert PWM dimming signals into analog dimming
signals.
Other protection features include adjustable output over
voltage protection, PWM switch current limit and thermal
shutdown.
Features
z Wide Operation Voltage Range : 7V to 28V
z Programmable Channel Current
z 3% Current Matching Accuracy between Channels
z Adjustable Switching Frequency
z Easy Analog and Digital Dimming Control
z Adjustable Soft-Start
z Adjustable Output Over Voltage Protection
z Under Voltage Lockout and Thermal Shutdown
z SOP-24 package
z RoHS Compliant and Halogen Free
Applications
z Building and Street Lighting
z LED TV Backlight
z LED Monitor Backlight
z Industrial Display Backlight
Simplified Application Circuit
V_IN
R3
V_CC
L1
C_IN
C_VCC
RT8489
VCC
GATE
ISENSE
RSET
R_VC
C_VC
R_SET
VC
SS
C_SS
LED1
GATE1
SENSE1
DCTL
LED4
GATE4
ACTL SENSE4
GND
Copyright ©2012 Richtek Technology Corporation. All rights reserved.
DS8489-00 November 2012
D1
M_SW
C_OUT
……
R_SENSE
V_OUT
4 x N LEDs
M1
R_S1
M4
R_S4
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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