®
RT4533/A
Asynchronous Boost Converter for 10 WLEDs
General Description
The RT4533/A is a highly integrated LED driver IC capable
of driving 10 WLEDs in series. It is composed of a current
mode Boost converter integrated with a 36.5V/1.2A power
switch.
The RT4533/A supports a wide input voltage range from
2.5V to 5.5V and runs at a fixed frequency of 1.1MHz.
The LED current is set via an external resistor and the
feedback voltage is regulated to 200mV / 300mV.
For brightness dimming, the RT4533/A supports PWM
dimming which determines the feedback reference voltage.
Features
2.5V to 5.5V Input Voltage Range
36.5V Open LED Protection for 10 WLEDs
PWM Dimming Brightness Control
200mV / 300mV Reference Voltage with
±
2%
Accuracy
1.1MHz Switching Frequency
Built-In Soft-Start
Over-Temperature Protection
Internal Compensation
Current Limit
RoHS Compliant and Halogen Free
Applications
Ordering Information
RT4533/A
Package Type
J6 : TSOT-23-6
Lead Plating System
G : Green (Halogen Free and Pb Free)
Feedback Voltage
RT4533 : 200mV
RT4533A : 300mV
Note :
Richtek products are :
½
Cellular Phones
Digital Cameras
Probable Instruments
Marking Information
RT4533GJ6
0R= : Product Code
0R=DNN
DNN : Date Code
RT4533AGJ6
1L= : Product Code
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.
1L=DNN
DNN : Date Code
½
Simplified Application Circuit
L
D
V
OUT
LX
V
IN
VIN
VOUT
RT4533/A
…
Enable
EN
GND
FB
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4533/A-02
September 2015
www.richtek.com
1
RT4533/A
Pin Configurations
(TOP VIEW)
VIN VOUT EN
6
5
4
2
3
LX GND FB
TSOT-23-6
Functional Pin Description
Pin No.
1
2
3
4
5
6
LX
GND
FB
EN
VOUT
VIN
Pin Name
Switch Node.
Ground.
Feedback Voltage Input. Put a resistor to GND to setting the current.
Enable Control Input (PWM Dimming).
Output Voltage Pin.
Supply Voltage Input.
Pin Function
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS4533/A-02
September 2015
RT4533/A
Function Block Diagram
VIN
LX
UVLO
OVP
VOUT
Internal
Compensation
-
OCP
OTP
PWM
Logic Control,
Minimum On
Time
Current-
Sense
Driver
GND
Slope
Compensation
LPF
Enable
Logic
Shutdown
20ms
PWM
Oscillator
Reference
Voltage
EA
GM
-
+
V
REF
Bias
Current
FB
Operation
The RT4533/A is a constant frequency, current mode
Boost LED driver. In normal operation, the N-MOSFET is
turned on when the PWM Control circuit is set by the
oscillator and is turned off when the current comparator
resets the PWM Control circuit. While the N-MOSFET is
turned off, the inductor current conducts through the
external diode.
UVLO
When the input voltage is lower than the UVLO threshold
(2.37V typ.), the driver will turn off. There is a 80mV for
the UVLO hysteresis control.
Soft-Start
When the device is enabled, the Comp ramps up to the
target voltage in a specific time. This ensures that the
output voltage rises slowly to reduce the input inrush
current.
EN Dimming
The EN pin is used for the control input for both PWM
dimming mode and digital dimming mode. Shutdown delay
when the EN voltage is logic low for more than specific
time, the driver will be shut down.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
DS4533/A-02
September 2015
+
Internal
Soft-Start
+
EN
OCP
The driver provides cycle-by-cycle current limit function
to control the current on power switch. The boost switch
turns off when the inductor current reaches this current
threshold and it remains off until the beginning of the next
switching cycle. This protects the RT4533/A and external
component under overload conditions.
OVP
The Over Voltage Protection is detected by a resistor
divider circuit from VOUT.
Once VOUT goes over the OVP voltage, LX pin stops
switching and the power N-MOSFET will be turned off.
Then, the VOUT will be discharged by external resistor.
OVP will be released until EN goes from Lo to Hi again.
OTP
As the die temperature is higher than 160°C, the chip
also will enter protection mode. The power MOSFET will
be turned off during protection mode to prevent abnormal
operation. The device is released from shutdown
automatically when the junction temperature decreases
by 15°C.
is a registered trademark of Richtek Technology Corporation.
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3
RT4533/A
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6V
−0.3V
to (V
IN
+ 0.3V)
−0.3V
to 38V
−0.3V
to 40V
0.5W
VIN ----------------------------------------------------------------------------------------------------------------------
EN, FB to GND -------------------------------------------------------------------------------------------------------
LX to GND -------------------------------------------------------------------------------------------------------------
V
OUT
to GND ----------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
TSOT-23-6 -------------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 2)
TSOT-23-6,
θ
JA
------------------------------------------------------------------------------------------------------- 197.4°C/W
Junction Temperature ----------------------------------------------------------------------------------------------- 150°C
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------- 260°C
Storage Temperature Range --------------------------------------------------------------------------------------
−65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------- 200V
Recommended Operating Conditions
(Note 4)
Supply Input Voltage, V
IN
------------------------------------------------------------------------------------------ 2.5V to 5.5V
Junction Temperature Range --------------------------------------------------------------------------------------
−40°C
to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------
−40°C
to 85°C
Electrical Characteristics
(V
IN
= 3.6V, C
IN
= 4.7μF, C
OUT
= 1μF, L = 22μH, f
SW
= 1.1MHz, T
A
= 25°C, unless otherwise specified)
Parameter
Power Supply
IC Operating Current (switching)
Symbol
I
Q_SW
I
SD
UVLO
U
VLO_hys
V
IH
V
IL
R
EN
T
off
T
High_Min
T
Low
R
comp
D
pwm min
f
PWM
Test Conditions
V
FB
= 0V
V
FB
= 0.4V
EN = GND
VIN Rising Edge
VIN Falling Edge
Min
0.25
0.25
--
2.25
--
Typ
0.8
0.35
0.3
2.37
80
Max
1.5
0.5
1
2.5
--
Unit
mA
mA
A
V
mV
IC Quiescent Current (non-switching) I
Q
VIN Pin Shutdown Current
Under-Voltage Lockout Threshold,
Under-Voltage Lockout Hysteresis
Enable and Reference Control
EN Input Voltage
Logic-High
Logic-Low
1.4
--
--
20
0.5
1
--
--
5
--
--
300
--
--
--
7
3
--
--
0.4
--
--
--
10000
--
--
100
V
k
ms
s
s
M
%
kHz
EN Pull Low Resistance
EN Minimum Shut down Pulse Width
EN Minimum Logic High Pulse Width
EN Minimum logic low pulse width
Internal Comp Resistance
PWM Minimum Duty
PWM Frequency
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS4533/A-02
September 2015
RT4533/A
Parameter
Voltage And Current Control
Feedback Regulation Voltage
Feedback Pin Bias Current
Oscillator Frequency
Maximum Duty Cycle
Power Switch
N-MOSFET On-Resistance
OC and OLP
Peak N-MOSFET Current Limit
Open LED Protection Threshold
Thermal Shutdown
Thermal Shutdown Threshold
Thermal Shutdown Hysteresis
T
SD
T
SD
--
--
160
15
--
--
°C
°C
I
LIM
OVP
1.0
35
1.2
36.5
1.4
38
A
V
R
DS(ON)
V
IN
= 3.6V
--
0.4
0.7
RT4533
RT4533A
V
FB
I
FB
f
SW
D
MAX
196
294
--
0.99
--
200
300
--
1.1
93
204
306
0.1
1.21
--
mV
A
MHz
%
Symbol
Test Conditions
Min
Typ
Max
Unit
Note 1.
Stresses beyond those listed
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are
stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2.
θ
JA
is measured at T
A
= 25°C on a high effective thermal conductivity four-layer test board per JEDEC 51-7.
Note 3.
Devices are ESD sensitive. Handling precaution is recommended.
Note 4.
The device is not guaranteed to function outside its operating conditions.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4533/A-02
September 2015
www.richtek.com
5
