®
RT4532
High Efficiency Backlight LED Driver
General Description
The RT4532 is a high-efficiency LED driver for backlight
applications. An asynchronous boost converter with an
internal Schottky diode and a current source driver are
designed to support 6LED/channel with wide input voltage
range from 2.5V to 5.5V.
An I
2
C interface can provide easy backlight control in fast
and high speed mode. The RT4532 supports linear
mappings with 256 steps to setup the brightness of
backlight LEDs. It also supports PWM dimming to adjust
the brightness.
The RT4532 provides complete protection functions such
as input under-voltage lockout, over-current, output over-
voltage and over-temperature protection. The OVP
threshold voltage can be set at 16V and 24V for different
applications. The RT4532 is available in the
WL-CSP-10B 0.87x2.07 package.
Features
Input Voltage Range : 2.5V to 5.5V
Internal Schottky Diode
Fast-speed mode I
2
C Compatible Interface
Drive Up to 6 WLEDs in 4 String
External PWM Brightness Control
550k/1.1MHz Switching Frequency
Built-in Internal Soft-Start
I
2
C Programmable 256 Steps Linear Current
Regulation
Up to 85% Efficiency with Small Magnetics
Programmable 16V/24V OVP
Current Accuracy
±
5% and Current Balance
±
3%
UVLO, OVP, OCP, OTP Protection
Shutdown Current : < 1μA
μ
Temperature Range :
−
40°C to 85°C
°
°
Applications
Ordering Information
RT4532
Package Type
WSC : WL-CSP-10B 0.87x2.07 (BSC)
Note :
Richtek products are :
½
Cellular Phones
Digital Cameras
PDAs and Smart Phones
Portable Instruments
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.
½
Simplified Application Circuit
L
LX
V
IN
C
IN
Enable
EN
PWM
SCL
SDA
GND
FB1
FB2
VIN
……
……
……
……
x6
RT4532
VOUT
C
OUT
V
OUT
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4532-01 August 2015
www.richtek.com
1
RT4532
Pin Configuration
(TOP VIEW)
2KW
LX
A1
B1
C1
D1
E1
A2
B2
C2
D2
E2
Marking Information
2K : Product Code
W : Date Code
GND
VIN
EN
SCL
FB1
VOUT
PWM
SDA
FB2
WL-CSP-10B 0.87x2.07(BSC)
Functional Pin Description
Pin No.
A1
A2
B1
B2
C1
C2
D1
D2
E1
E2
Pin Name
LX
GND
VOUT
VIN
PWM
EN
SDA
SCL
FB2
FB1
Ground.
Power output of the asynchronous boost converter for backlight LEDs. Connect a
1
F or larger ceramic capacitor from VOUT to ground.
Power input. Connect this pin to the input power supply voltage. Connect a 10F
or larger ceramic capacitor from the VIN to ground.
PWM dimming input for backlight LED.
Enable control input (active high). The chip is in shutdown mode when the EN pin
is low.
I
2
C serial data input/output. An external pull-up resistor is required.
I
2
C serial clock input. An external pull-up resistor is required.
Single output 2 for backlight LED.
Single output 1 for backlight LED.
Pin Function
Switch node of boost converter. Connect an inductor between LX and VIN.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS4532-01 August 2015
RT4532
Functional Block Diagram
VIN
FB1
FB2
LX
PWM
PWM2DC
V
REF
Current
Source Gen.
V
FB
+
-
LEDs
OTP
OVP
VOUT
SCL
SDA
EN
Digital
Control
EA
PWM
Logic
VSLOPE
OCP
GND
Operation
The RT4532 is a high efficiency solution with 24 WLEDs
in 4 parallels 6 series for backlight applications. The
RT4532 optimizes the feedback regulation voltage to
provide up to 85% high efficiency with as high as 8bits
resolution application.
Linear Brightness Dimming
The RT4532 is built-in a I
2
C 8-bit resolution brightness
control with maximum 20mA/40mA selection.
Reg0x02<3> corresponds to full-scale LED current control.
Reg0x04 sets 8bits resolution brightness dimming.
PWM Brightness Dimming
Besides programmable built-in I C backlight LED current
control, the RT4532 features a built-in PWM dimming
current control by setting Reg0x02<6> to 1, offering a
linear current dimming by external clock source. In order
to guarantee the PWM dimming resolution, recommending
dimming frequency have to be operated at range of 400Hz
to 20kHz.
2
OCP Protection
The RT4532 features a 1.2A current limitation. Once
detecting current level over current limitation, the RT4532's
LX witching will be forced off to avoid large current damage.
OTP Protection
The over-temperature protection function will be latched
at shutdown status when the junction temperature
exceeds 140°C for 2ms. After re-power on sequence, the
converter will automatically resume switching.
OVP Protection
The over-voltage protection function monitors the output
voltage via the VOUT pin voltage. The OVP threshold
voltage is 24V/16V by selecting Reg0x02<7>. Once the
LED is open, the output voltage reaches the OVP
threshold, the driver will be shut down.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS4532-01 August 2015
www.richtek.com
3
RT4532
Absolute Maximum Ratings
(Note 1)
−0.3V
to 6V
−0.3V
to 26V
−0.3V
to 26V
−0.3V
to 26V
−0.3V
to 6V
Supply Input Voltage, VIN -----------------------------------------------------------------------------------------------
Boost Output Voltage, VOUT -------------------------------------------------------------------------------------------
Switching Voltage, LX ----------------------------------------------------------------------------------------------------
Current Source Voltage, FB1, FB2 ------------------------------------------------------------------------------------
Other Pins, EN, PWM, SCL, SDA ------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WL-CSP-10B 0.87x2.07 (BSC) ---------------------------------------------------------------------------------------- 1W
Package Thermal Resistance (Note 2)
WL-CSP-10B 0.87x2.07 (BSC),
θ
JA
---------------------------------------------------------------------------------- 99.6°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
Junction Temperature ----------------------------------------------------------------------------------------------------- 150°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, VIN ----------------------------------------------------------------------------------------------- 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
= 10μF, C
OUT
= 1μF, L = 10μH, T
A
= 25°C, unless otherwise specified)
Parameter
Input Power Supply
Input Supply Voltage
VIN Quiescent Current
Shutdown Current
Symbol
V
IN
I
Q
I
SHDN
V
UVLO
V
UVLO
Test Conditions
Min
2.5
Typ
--
0.6
1
--
150
Max
5.5
--
3
2.3
--
Unit
V
mA
A
V
mV
PWM, No Switching
V
IN
= 4.2V, EN = GND
V
IN
Falling, Check I
Q
< 200A
After UVLO, V
IN
Rising,
Until I
Q
> 200µA
FB1, FB2 = 0.15V, I
FB1
= I
FB2
= 20mA
FB1, FB2 = 0.15V, I
FB1
= I
FB2
= 20mA
Reg0x03 [6] = 1
FB1 = FB2 = 0V, check MAX duty
Reg0x03 [5:0] = 111111
--
--
--
--
Under-Voltage Lockout
Threshold
Under-Voltage Lockout
Hysteresis
Accuracy of Output Current
Matching of Output Current
Oscillator and Timing
Operating Frequency
Maximum Duty Cycle
Brightness Ramp Rate
Backlight LED Current Source
I
LED_ACC
I
LED_MAT
f
SW
D
MAX
T
RAMP
5
3
0.88
90
--
--
1.1
95
5
3
1.32
--
%
%
MHz
%
ms
209.72 262.14 314.58
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS4532-01 August 2015
RT4532
Parameter
Power Switch
N-MOSFET On-Resistance
N-MOSFET Current Limit
N-MOSFET Leakage
Current
Protection Function
Over Voltage Protection
Thermal Shutdown
OVP
T
SD
Reg0x02 [7] = 0
Reg0x02 [7] = 1
Thermal latch
14
23
--
16
24
150
18
25
--
V
V
°C
Symbol
Test Conditions
Min
100
1
LX = 24V, No Switching
--
Typ
200
1.2
--
Max
300
1.4
1
Unit
m
A
A
R
DS(ON)_N
V
IN
= 3.6V
I
OCP
I
LEAK
Threshold
EN Input
Voltage
Logic Control
Logic-High
Logic-Low
Logic-High
Logic-Low
Logic-High
Logic-Low
Logic-High
Logic-Low
V
ENH
V
ENL
V
PWML
V
PWML
V
SCLH
V
SCLL
V
SDAH
V
SDAL
1.05
--
1.05
--
1.3
--
1.3
--
--
--
f
SCL
--
--
--
--
--
--
--
--
--
400
400
--
--
0.4
--
0.4
--
0.4
--
0.4
--
--
400
V
V
V
V
k
k
kHz
PWM Input
Voltage
SCL Input
Voltage
SDA Input
Voltage
EN Pull-Down Resistance
PWM Pull-Down Resistance
Clock Frequency of SCL
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.
θ
JC
is
measured at the exposed pad of the package.
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.
DS4532-01 August 2015
www.richtek.com
5
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