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RT8301
8-CH Constant Current LED Driver for Display Backlight
General Description
The RT8301 is a 8-CH constant current sink LED drivers with Dynamic Headroom Control (DHC) function. RT8301 can provide well current matching ability, adjustable VSET to choose the suitable dropout voltage across the MOS / BTJ. Beside that, DHC will provide the stable VFB dimming, thus voltage ripple is kept as small even during the dimming.
The RT8301 provides four channel constant currents with less than 3% differences in output current value among the 8-CH and ICs respectively. The constant current is adjustable by each channel external resistor (RISET). The LED brightness can also be adjusted via the EN/PWM pin with PWM dimming duty from 1% to 100%. The RT8301 can operate with external components for high current applications.
The DHC function generates feedback signal to DC/DC control loop and regulate the output voltage. When RT8301 selects the LED string with the highest forward voltage, and then the COMP is defined according to that particular string. The COMP voltage is then compared with the voltage of VSET to determine the voltage level of VFB, which therefore control the switching of the primary controller.
RT8301's protection features include Short LED Protection (SLP), Open LED Protection (OLP) and Over Temperature Protection (OTP). When any channel triggers protection function, LED will be turned off and the FAULT pin will pull low.
The RT8301 is available in SOP-24 package to achieve optimized solution for PCB space.
Simplified Application Circuit
VOUT
COUT
8 x NLEDs
DSL11
DSL18
VCC
VSET
RSET1 RSET2
CVCC1 FAULT
RT8301 VCC
FAULT RSLP
SLP
Q1 ZD2
……
VSET VFB
SLP
VCC COMP RCOMP
COMP
CCOMP
DC11 D1
DC18 ……
COMP1
RFAULT VCC
FAULT OUT1 CS1
M11
……
PWM Signal
EN/PWM OUT8
CS8 GND
…… …… RS11
M18 RS18
Copyright ©2013 Richtek Technology Corporation. All rights reserved. DS8301-03 April 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com 1
RT8301
Features
z Wide Input Supply Voltage Range : 5V to 24V z Adjustable Channel Current z 3% Current Sense Amplifier Input Offset z VCC Under Voltage Lockout z Thermal Shutdown z Adjustable Dynamic Headroom Control (DHC)
Function z LED Open/Short Protection z RoHS Compliant and Halogen Free
Applications
z LCD TV, MNT Display Backlight z DC/DC or AC/DC LEDDriver Application z General Purpose Constant Current Source z Architectural and Decorative LED Lighting z LED Street Lighting
Marking Information
RT8301 GSYMDNN
RT8301GS : Product Number YMDNN : Date Code
Ordering Information
RT8301
Package Type S : SOP-24
Note :
Lead Plating System G : Green (Halogen Free and Pb Free)
Richtek products are :
` RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
` Suitable for use in SnPb or Pb-free soldering processes.
Pin Configurations
(TOP VIEW)
VFB COMP EN/PWM
VCC OUT1
CS1 OUT3
CS3 OUT5
CS5 OUT7
CS7
2 3 4 5 6 7 8 9 10 11 .