RT9284A/B
Tiny Package, High Performance, Constant Current
Switching Regulator for White LED
General Description
The RT9284A/B is a compact, high efficient and high
integration LED driver. Internal 22V MOSFET can support
2 to 5 White LEDs for backlighting and camera flashing.
Highly integration and internal compensation network
minimizes as 5 external component counts. Optimized
operation frequency can meet the requirement of small
LC filters value and low operation current with high
efficiency. Internal soft start function can reduce the inrush
current. Tiny package type of TSOT-23-5 and TSOT-23-6
packages provide the best solution for PCB space saving
and total BOM cost.
Features
V
IN
Operating Range : 2.7V to 5.5V
Maximum Output Voltage up to 20V
Dimming with Zero-inrush and Wide Frequency
Range of 100 to 100kHz
Over Voltage Protection
Output Current up to 100mA at V
OUT
= 12V.
Zero Shutdown Supply Current
Minimize the External Component
Small LC Filter
Internal Soft Start
RoHS Compliant and 100% Lead (Pb)-Free
Ordering Information
RT9284 (-
)
Package Type
J5 : TSOT-23-5
J6 : TSOT-23-6
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with
Commercial Standard)
OVP Voltage
15 : 15V
20 : 20V
FB Voltage
A : 1.235V
B : 0.25V
Note :
Richtek Pb-free and Green 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.
100% matte tin (Sn) plating.
Applications
Camera Flash White LED
Mobile Phone, Smart Phone LED Backlight
PDA LED Backlight
Digital Still Camera
Camcorder
Pin Configurations
TOP VIEW
VDD
5
1
LX
2
GND
EN
4
3
FB
TSOT-23-5
VDD OVP
6
1
LX
5
2
GND
EN
4
3
FB
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
TSOT-23-6
Note
: There is no pin1 indicator on top mark for
TSOT-23-6
type, and pin 1 will be lower left pin when reading top mark
from left to right.
DS9284A/B-05 August 2007
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RT9284A/B
Typical Application Circuit
L1
4.7uH to 22uH
V
IN
+
2.7V to 5.5V
D1
SS0520
OVP
15V
C2
1uF/16V
I
LED
C1
1uF
6
RT9284
1
LX
VDD
EN
GND
OVP
5
Dimming
Control
100Hz-100kHz
4
2
FB 3
R1
Figure 1. Application for Driving 3 Series WLEDs
L1
4.7uH to 22uH
V
IN
+
2.7V to 5.5V
D1
SS0520
OVP
18V
C2
1uF/25V
I
LED
C1
1uF
6
RT9284
1
LX
VDD
EN
GND
OVP
5
OVP 15V
R2
600k
Dimming
Control
100Hz-100kHz
4
2
FB 3
R1
Figure 2. Application for Driving 4 Series WLEDs
L1
4.7uH to 22uH
V
IN
+
2.7V to 5.5V
D1
SS0520
OVP
20V
C2
1uF/25V
I
LED
C1
1uF
6
RT9284B
1
LX
VDD
EN
GND
OVP
5
Dimming
Control
100Hz-100kHz
4
2
FB 3
V
FB
= 0.25V
R1
Figure 3. Application for Driving 5 Series WLEDs
L1
4.7uH to 22uH
V
IN
+
2.7V to 5.5V
D1
OVP
SS0520 15V
V
OUT
12V
R1
130k
C2
1uF/16V
C1
1uF
6
4
2
RT9284A
1
LX
VDD
EN
GND
OVP
5
FB 3
V
FB
= 1.235V
R2
15k
Figure 4. Application for Constant Output Voltage
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DS9284A/B-05 August 2007
RT9284A/B
Pin Description
Pin No.
TSOT-23-5 TSOT-23-6
1
2
3
1
2
3
LX
GND
FB
Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track
area to reduce EMI.
Ground Pin
Feedback Reference Voltage Pin. Series connect a resistor between WLED
and ground as a current sense. Sense the current feedback voltage to set
the current rating.
Chip Enable (Active High). Voltage sensing input to trigger the function of
over voltage protection. Note that this pin is high impedance. There should
be a pull low 100kΩ resistor connected to GND when the control signal is
floating.
Over Voltage Protection Pin. Voltage sensing input to trigger the function of
over voltage protection. Leave it unconnected to disable this function.
Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input
noise.
Pin Name
Pin Function
4
4
EN
--
5
5
6
OVP
VDD
Function Block Diagram
1.2MHz OSC
VDD
Current Bias
BandGap
Protection Circuit
OVP
OVP
UVLO
Timer
5ms
+
-
Buffer
+
-
EN
Soft Start
V
REF
FB
GND
ibias
V
REF
OCP
750mA
PWM
Logic
LX
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RT9284A/B
Absolute Maximum Ratings
(Note 1)
−0.3V
to 7V
−0.3V
to 22V
−0.3V
to 22V
−0.3V
to 6V
0.455W
0.455W
Supply Input Voltage ------------------------------------------------------------------------------------------------------
LX Input Voltage -----------------------------------------------------------------------------------------------------------
OVP Voltage ----------------------------------------------------------------------------------------------------------------
The Other Pins -------------------------------------------------------------------------------------------------------------
Power Dissipation, P
D
@ T
A
= 25°C
TSOT-23-5 -------------------------------------------------------------------------------------------------------------------
TSOT-23-6 -------------------------------------------------------------------------------------------------------------------
Package Thermal Resistance (Note 4)
TSOT-23-5,
θ
JA
------------------------------------------------------------------------------------------------------------- 220°C/W
TSOT-23-6,
θ
JA
------------------------------------------------------------------------------------------------------------- 220°C/W
Lead Temperature (Soldering, 10 sec.) ------------------------------------------------------------------------------- 260°C
Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
Storage Temperature Range --------------------------------------------------------------------------------------------
−
65°C to 150°C
ESD Susceptibility (Note 2)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions
(Note 3)
Supply Input Voltage ------------------------------------------------------------------------------------------------------ 2.7V to 5.5V
Junction Temperature Range --------------------------------------------------------------------------------------------
−
40°C to 125°C
Ambient Temperature Range --------------------------------------------------------------------------------------------
−
40°C to 85°C
Electrical Characteristics
(V
IN
= 3.7V, T
A
= 25°C unless otherwise specified)
Parameter
System Supply Input
Operation voltage Range
Under Voltage Lock Out
Quiescent Current
Supply Current
Shut Down Current
Line Regulation
Oscillator
Operation Frequency
Maximum Duty Cycle
Dimming Frequency
Reference Voltage
Symbol
Test Condition
Min
Typ
Max
Units
V
DD
V
DD
I
DD
I
DD
I
DD
FB = 1.5V, No switch
FB = 0V, Switch
V
EN
< 0.4V
V
IN
: 3.0~4.3V
2.7
1.8
50
0.1
--
--
--
2.2
300
2
--
3
5.5
2.5
1000
3
1
--
V
V
uA
mA
uA
%
f
OSC
0.9
85
100
1.2
--
--
1.5
--
100k
MHz
%
Hz
RT9284A
Feedback Voltage
(Note 5)
RT9284B
1.173
0.237
1.235
0.25
1.296
0.263
V
V
To be continued
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DS9284A/B-05 August 2007
RT9284A/B
Parameter
MOSFET
On Resistance of MOSFET
Protection
OVP Threshold
OVP Sink Current
OCP
Shut Down Voltage
Enable Voltage
V
EN
V
EN
for 2,3,4 WLEDs application
V
OVP
for 5 WLED application
14
19
--
--
--
1.5
15
20
5
750
--
--
16
21
--
--
0.4
--
V
V
μA
mA
V
V
R
DS(ON)
--
0.75
--
Ω
Symbol
Test Condition
Min
Typ
Max
Units
Note 1.
Stresses listed as the above
“Absolute
Maximum Ratings” may cause permanent damage to the device. These are for
stress ratings. 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 for extended
periods may remain possibility to affect device reliability.
Note 2.
Devices are ESD sensitive. Handling precaution recommended.
Note 3.
The device is not guaranteed to function outside its operating conditions.
Note 4.
θ
JA
is measured in the natural convection at T
A
= 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 5.
Floating the OVP pin to disable OVP function.
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