®
RT8511B
43V Asynchronous Boost WLED Driver
General Description
The RT8511B is an LED driver IC that can support up to
10 WLED in series. It is composed of a current mode
boost converter integrated with a 43V/2.2A power switch
running at a fixed 500kHz frequency and covering a wide
VIN range from 2.7V to 24V.
The white LED current is set with an external resistor, and
the feedback voltage is regulated to 200mV (typ.). During
operation, the LED current can be controlled by the PWM
input signal in which the duty cycle determines the
feedback reference voltage.
For brightness dimming, the RT8511B is able to maintain
steady control of the LED current. Therefore, no audible
noises are generated on the output capacitor. The RT8511B
also has programmable over voltage pin to prevent the
output from exceeding absolute maximum ratings during
open LED conditions. The RT8511B is available in
WDFN-8L 2x2 package.
Features
Wide Input Voltage Range : 2.7V to 24V
High Output Voltage : up to 43V
Direct PWM Dimming Control and Frequency from
100Hz to 8kHz
Internal Soft-Start and Compensation
200mV Reference Voltage
PWM Dimming with Internal Filter
Programmable Over Voltage Protection
Over Temperature Protection
Current Limit Protection
Thin 8-Lead WDFN Package
RoHS Compliant and Halogen Free
Applications
UMPC and Notebook Computer Backlight
GPS, Portable DVD Backlight
Ordering Information
RT8511B
Package Type
QW : WDFN-8L 2x2 (W-Type)
Lead Plating System
G : Green (Halogen Free and Pb Free)
Note :
Richtek products are :
½
Pin Configurations
(TOP VIEW)
OVP
FB
DIMC
GND
1
2
3
4
8
7
6
5
9
EN
PWM
VIN
LX
WDFN-8L 2x2
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.
Marking Information
0F : Product Code
½
0FW
W : Date Code
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8511B-05 February 2015
GND
www.richtek.com
1
RT8511B
Typical Application Circuit
V
IN
4.2V to 24V
6 VIN
L
10µH
RT8511B
LX 5
OVP
8 EN
7 PWM
3
DIMC
C
DIMC
1µF
FB 2
GND
4, 9 (Exposed Pad)
R
SET
3.3
1
R1
100k
V
OUT
D
R2
3.3M
C
OUT
1µF x 2
C
IN
1µF x 2
Chip Enable
:
:
:
:
:
:
:
:
:
: WLEDs
:
:
PWM
100Hz to 8kHz
Figure 1. Typical Application Circuit of Normal Operation
L
10µH
C
LED
1µF x 2
C
IN
1µF
6 VIN
8 EN
7 PWM
3
DIMC
C
DIMC
1µF
FB 2
GND
4, 9 (Exposed Pad)
R
SET
3.3
RT8511B
LX 5
OVP
1
R1
100k
V
OUT
D
V
LED
2.7V to 24V
V
IN
2.7V to 4.2V
Chip Enable
R2
3.3M
C
OUT
1µF x 2
:
:
:
:
:
:
:
:
:
: WLEDs
:
:
PWM
100Hz to 8kHz
Figure 2. Typical Application Circuit of Low Voltage Operation
Functional Pin Description
Pin No.
1
2
3
4
5
6
7
8
9 (Exposed Pad)
Pin Name
OVP
FB
DIMC
GND
LX
VIN
PWM
EN
GND
Pin Function
Over Voltage Protection for Boost Converter. The detecting threshold is 1.2V.
Feedback. Connect a resistor between this pin and GND to set the LED current.
PWM Filter. Filter the PWM signal to a DC voltage.
Ground.
Switch Node for Boost Converter.
Power Supply Input.
Dimming Control Input.
Chip Enable (Active High) for Boost Converter.
The exposed pad must be soldered to a large PCB and connected to AGND for
m aximum power dissipation.
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
2
DS8511B-05 February 2015
RT8511B
Function Block Diagram
OVP
LX
VIN
EN
OSC
S
+
-
Q
1.2V
OTP
OCP
R
Q
PWM
Controller
PWM
DIMC
FB
D/A
Dimming
-
+
+
-
GND
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS8511B-05 February 2015
www.richtek.com
3
RT8511B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 26.5V
−0.3V
to 48V
−0.3V
to 48V
−1V
to 48V
VIN, EN, PWM, DIMC to GND ------------------------------------------------------------------------------------------
FB, OVP to GND ----------------------------------------------------------------------------------------------------------
LX to GND ------------------------------------------------------------------------------------------------------------------
< 500ns ----------------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
WDFN-8L 2x2 -------------------------------------------------------------------------------------------------------------- 0.833W
Package Thermal Resistance (Note 2)
WDFN-8L 2x2,
θ
JA
--------------------------------------------------------------------------------------------------------- 120°C/W
WDFN-8L 2x2,
θ
JC
---------------------------------------------------------------------------------------------------------
Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------------------
Junction Temperature -----------------------------------------------------------------------------------------------------
Storage Temperature Range --------------------------------------------------------------------------------------------
8.2°C/W
260°C
150°C
–65°C
to 150°C
ESD Susceptibility (Note 3)
HBM (Human Body Model) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Model) ----------------------------------------------------------------------------------------------------- 200V
(Note 4)
Recommended Operating Conditions
Supply Input Voltage, V
IN
------------------------------------------------------------------------------------------------ 2.7V to 24V
Junction Temperature Range --------------------------------------------------------------------------------------------
−
40°C to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------------
−
40°C to 85°C
Electrical Characteristics
(V
IN
= 4.5V, T
A
= 25°C, unless otherwise specified)
Parameter
VIN Quiescent Current
VIN Shutdown Current
Control Input
Logic-High
EN, PWM
Threshold Voltage Logic-Low
EN Sink Current
Shutdown Delay
PWM Dimming Frequency
Boost Converter
Switching Frequency
LX On Resistance
(N-MOSFET)
Minimum ON Time
Maximum Duty Cycle
Symbol
I
Q
I
Q_SW
I
SHDN
Test Conditions
V
FB
= 1.5V, No Switching
V
FB
= 0V, Switching
V
IN
= 4.5V, V
EN
= 0V
Min
--
--
--
Typ
725
--
1
Max
--
2.2
4
Unit
A
mA
A
V
IH
V
IL
I
IH
t
SHDN
V
IN
= 2.7V to 24V
V
IN
= 2.7V to 24V
V
EN
= 3V
EN high to low
1.6
--
1
52
0.1
--
--
--
64
--
--
0.8
10
80
8
V
A
ms
kHz
f
OSC
R
DS(ON)
V
IN
= 2.7V to 24V
V
IN
> 5V
0.4
--
--
0.5
0.4
60
92
0.6
0.6
--
--
MHz
ns
%
D
MAX
V
FB
= 0V, Switching
--
Copyright
©
2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS8511B-05 February 2015
RT8511B
Parameter
LED Current
Minimum PWM Dimming Duty
Cycle
Feedback Voltage
Fault Protection
LX Current Limit
Over Voltage Protection
Threshold
Thermal Shutdown
Temperature
Thermal Shutdown Hysteresis
I
LIM
V
OVP
T
SD
T
SD
1.66
1.14
--
--
2.2
1.2
160
30
2.74
1.26
--
--
A
V
°C
°C
D
MIN
V
FB
Dimming Freq. = 100Hz to 8kHz
1
195
--
200
--
205
%
mV
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.
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.
DS8511B-05 February 2015
www.richtek.com
5
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