LED Driver. RT8474 Datasheet

RT8474 Driver. Datasheet pdf. Equivalent

RT8474 Datasheet
Recommendation RT8474 Datasheet
Part RT8474
Description High Voltage Multiple-Topology LED Driver
Feature RT8474; ® RT8474 High Voltage Multiple-Topology LED Driver with Dimming Control General Description The RT.
Manufacture Richtek
Datasheet
Download RT8474 Datasheet




Richtek RT8474
®
RT8474
High Voltage Multiple-Topology LED Driver with Dimming Control
General Description
The RT8474 is a current-mode LED driver supporting wide
input voltage range from 4.5V to 50V and output voltage
up to 50V. With internal 500kHz operating frequency, the
size of the external PWM inductor and input/output
capacitors can be minimized. High efficiency is achieved
by a 100mV current sensing control. LED dimming control
can be done from either analog or PWM signal. The RT8474
provides an internal soft-start function to avoid inrush
current and thermal shutdown to prevent the device from
overheat.
The RT8474 is available in the SOP-8 (Exposed pad)
package.
Ordering Information
RT8474
Package Type
SP : SOP-8 (Exposed-Option 2)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
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.
Features
High Voltage : VIN Up to 50V, VOUT Up to 50V
Support Multiple-Topologies (Buck / Boost / Buck-
Boost)
Built-In 2A Power Switch
Current-Mode PWM Control
500kHz Fixed Switching Frequency
Analog or PWM Control Signal for LED Dimming
Internal Soft-Start to Avoid Inrush Current
Under-Voltage Lockout
Thermal Shutdown
RoHS Compliant and Halogen Free
Applications
Desk Lights and Room Lighting
Industrial Display Backlight
Marking Information
RT8474
GSPYMDNN
RT8474GSP : Product Number
YMDNN : Date Code
Pin Configurations
(TOP VIEW)
VCC
ISP
ISN
NC
8
27
GND
36
9
45
CREG
SW
CTL
VC
SOP-8 (Exposed Pad)
Simplified Application Circuit
VIN
R3 C1
Analog Dimming
or PWM Dimming
C5
RT8474
VCC
ISP
ISN
CTL
R1
R2
C2
VC
SW
CREG
C3
GND
D1
RSENSE
L1
C4
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8474-04 April 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1



Richtek RT8474
RT8474
Functional Pin Description
Pin No.
Pin Name
Pin Function
1 VCC
2 ISP
3 ISN
4 NC
Supply Voltage Input. For good bypass, connect a low ESR capacitor
between this pin and GND.
Positive Current Sense Input.
Negative Current Sense Input. Voltage threshold between ISP and ISN is
100mV.
No Internal Connection.
5 VC
6 CTL
7 SW
8 CREG
9 (Exposed Pad) GND
Compensation Node for Current Loop.
Analog Dimming Control Input. Effective programming range is 0.2V to
1.2V.
Switch Node of the PWM Converter.
Regulator Output for Internal Circuit. Place a 1F capacitor to stabilize the
5V output regulator.
Ground. The exposed pad must be soldered to a large PCB and connected
to GND for maximum power dissipation.
Function Block Diagram
VCC
-
4.5V +
OSC
S
R
R
SW
5V
LDO
CREG
VC
Soft-Start
-
GM
+
+
-
ISN
ISP
GND
Operation
CTL
The RT8474 is specifically designed to be operated in
Buck converter applications. This device uses a fixed
frequency, current-mode control scheme to provide
excellent line and load regulation. The control loop has a
current sense amplifier which senses the voltage between
the ISP and ISN pins and provides an output voltage at the
VC pin. A PWM comparator then turns off the internal
power switch when the sensed power switch current
exceeds the compensated VC pin voltage. The power
switch will not be reset by the oscillator clock in each
cycle. If the comparator does not turn off the switch in a
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
www.richtek.com
2
cycle, the power switch will be on for more than a full
switching period until the comparator is tripped. In this
manner, the programmed voltage across the sense
resistor is regulated by the control loop.
The current through the sense resistor is set by the
programmed voltage and the sense resistance. The voltage
across the sense resistor can be programmed by the
analog or digital signal at the CTL pin. The RT8474 provides
protection functions which include over- temperature, and
switch current limit to prevent abnormal situations.
is a registered trademark of Richtek Technology Corporation.
DS8474-04 April 2015



Richtek RT8474
RT8474
Absolute Maximum Ratings (Note 1)
Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------- 0.3V to 60V
SW Pin Voltage at Switching Off, ISP, ISN -------------------------------------------------------------------------- 0.3V to 60V
CREG Voltage -------------------------------------------------------------------------------------------------------------- 0.3V to 6V
CTL Voltage (Note 2) ---------------------------------------------------------------------------------------------------- 0.3V to 20V
Power Dissipation, PD @ TA = 25°C
SOP-8 (Exposed Pad) --------------------------------------------------------------------------------------------------- 3.44W
Package Thermal Resistance (Note 3)
SOP-8 (Exposed Pad), θJA ---------------------------------------------------------------------------------------------- 29°C/W
SOP-8 (Exposed Pad), θJC --------------------------------------------------------------------------------------------- 2°C/W
Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
Storage Temperature Range -------------------------------------------------------------------------------------------- 65°C to 150°C
ESD Susceptibility (Note 4)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions (Note 5)
Supply Input Voltage ------------------------------------------------------------------------------------------------------ 4.5V to 50V
Junction Temperature Range -------------------------------------------------------------------------------------------- 40°C to 125°C
Ambient Temperature Range -------------------------------------------------------------------------------------------- 40°C to 85°C
Electrical Characteristics
(VCC = 5V, CIN = 1μF, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Test Conditions
Overall
Regulator Output Voltage
Supply Current
VIN Under-Voltage Lockout
Threshold
Current Sense Amplifier
VCREG
IVCC
VUVLO
ICREG = 20mA
VC 0.4V
VIN Rising
VIN Falling
Input Threshold (VISP VISN)
Input Current
Input Current
Output Current
IISP
IISN
IVC
VCTL 1.25V
VISP = 24V
VISN = 24V
2.4V > VC > 0.3V
VC Threshold for CTL Switch Off
LED Dimming
Input Current of CTL Pin
ICTL 0.2V VCTL 1.2V
LED Current off Threshold at CTL VCTL_OFF
Min Typ Max Unit
4.5 5 5.5 V
-- -- 3 mA
-- 4.2 --
-- 3.8 --
V
97 100 103 mV
-- 200 -- A
-- 20 -- A
-- ±10 -- A
-- 0.4 --
V
-- 1 2 A
-- 0.2 0.25 V
Copyright ©2015 Richtek Technology Corporation. All rights reserved.
DS8474-04 April 2015
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3







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