LED Driver. RT4528 Datasheet

RT4528 Driver. Datasheet pdf. Equivalent

RT4528 Datasheet
Recommendation RT4528 Datasheet
Part RT4528
Description High Voltage Buck LED Driver
Feature RT4528; ® RT4528 High Voltage Buck LED Driver with Dimming Control General Description The RT4528 is a cur.
Manufacture Richtek Technology
Datasheet
Download RT4528 Datasheet




Richtek Technology RT4528
®
RT4528
High Voltage Buck LED Driver with Dimming Control
General Description
The RT4528 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 RT4528
provides an internal soft-start function to avoid inrush
current and thermal shutdown to prevent the device from
overheat.
The RT4528 is available in the SOP-8 (Exposed pad)
package.
Ordering Information
RT4528
Package Type
SP : SOP-8 (Exposed-Option 2)
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.
Features
High Voltage : VIN Up to 50V, VOUT Up to 50V
Built-In 3A 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
RT4528
GSPYMDNN
RT4528GSP : 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
Analog Dimming
or PWM Dimming
C1 RT4528
VCC
ISP
CTL ISN
RSENSE
R1
R2
C2
VC
SW
CREG
C3 GND
L1
D1
C4
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
DS4528-00 April 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1



Richtek Technology RT4528
RT4528
Functional Pin Description
Pin No.
Pin Name
Pin Function
1
VCC
Supply Voltage Input. For good bypass, connect a low ESR capacitor between
this pin and GND.
2 ISP Positive Current Sense Input.
3
ISN
Negative Current Sense Input. Voltage threshold between ISP and ISN is
100mV.
4 NC
No Internal Connection.
5 VC
Compensation Node for Current Loop.
6 CTL Analog Dimming Control Input. Effective programming range is 0.2V to 1.2V.
7 SW Switch Node of the PWM Converter.
8
CREG
Regulator Output for Internal Circuit. Place a 1F capacitor to stabilize the 5V
output regulator.
9 (Exposed Pad) GND
Ground. The exposed pad must be soldered to a large PCB and connected to
GND for maximum power dissipation.
Function Block Diagram
SW
VCC
-
4.5V +
OSC
S
R
R
5V
LDO
CREG
VC
Soft-Start
-
GM
+
+
-
ISN
ISP
GND
Operation
CTL
The RT4528 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 ©2014 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 RT4528 provides
protection functions which include over- temperature, and
switch current limit to prevent abnormal situations.
is a registered trademark of Richtek Technology Corporation.
DS4528-00 April 2014



Richtek Technology RT4528
RT4528
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 5.5V
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 ©2014 Richtek Technology Corporation. All rights reserved.
DS4528-00 April 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
3







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