RT9269
Tiny Package, High Efficiency, Constant Current LED Driver
General Description
The RT9269 is a compact, high efficient LED driver with
high flexibility of application configurations in charge pump
mode or in boost rectifier mode, delivering Tens of mA
constant output current for driving 1~4 white LED's.
The 0.25V low reference voltage minimized the power loss
across the current-setting resistor.
The wide applicable VDD range makes RT9269 suitable for
1 to 4 battery cell applications as well as being supplied
with 2.5/3.3/5/6V system powers. The 500kHz high
switching rate minimized the size of external components.
Besides, the 17μA low quiescent current together with high
efficiency maintains long battery lifetime.
The output current is set with 1 external resistor. And the
chip enable (EN) pin can be used for tuning the LED
brightness by controlling the ON/OFF duty with external
clock. RT9269 is provided in
SOT-23-6
package.
Features
0.25V Low Reference Voltage
17μA Quiescent (Switch-off) Supply Current
μ
Zero Shutdown Mode Supply Current
85% Efficiency
500kHz Fixed Switching Rate
Tuning LED brightness with EN Pin ON/OFF Duty
Small
SOT-23-6
Package
RoHS Compliant and 100% Lead (Pb)-Free
Applications
LED Module
Hand Held Panel
Compact Back Light Module
Small Battery Charger
Constant Current Source
Pin Configurations
(TOP VIEW)
FB VDD
6
5
Ordering Information
RT9269
Package Type
E : SOT-23-6
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
Note :
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.
LX
4
2
3
EN EXT GND
SOT-23-6
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
DS9269-12 April 2011
www.richtek.com
1
RT9269
Typical Application Circuit
D1
V
IN
C1
1uF
VDD
EXT
RT9269
To VDD
or
Duty Control
Brightness
EN
GND
FB
0.25V
C2
1uF
D2
C3
1uF
R1
15
R2
15
Figure 1. RT9269 drives single or parallel LED's in charge pump configuration
D1
V
IN
C1
1uF
VDD
EXT
RT9269
To VDD
or
Duty Control
Brightness
EN
GND
FB
0.25V
C2
1uF
D2
C3
1uF
R1
15
Figure 2. RT9269 drives 2 series connected LED's in charge pump configuration
V
IN
R1
1K
C2
10uF
L1
10uH to 100uH
Q1
C1
1uF
VDD
LX
RT9269
C3
10uF
To VDD
or
Duty Control
Brightness
EN
GND
FB
0.25V
R2
15
Figure 3. RT9269 drives 2~4 series connected LED's in boost rectifier configuration
Note: NICHIA NSCW100 is used for RT9269 LED parts.
www.richtek.com
2
DS9269-12 April 2011
RT9269
Functional Pin Description
Pin No. Pin Name
1
2
3
4
5
6
EN
EXT
GND
LX
VDD
FB
Pin Function
Chip Enable (Active High)
Output Pin for Configuring Charge Pump or Driving External NMOS
Ground
Pin for Switching
Input Positive Power Pin of RT9269
Feedback Input pin Internal Reference Voltage for the Error Amplifier is 0.25V.
Function Block Diagram
VDD
RT9269
EXT
LX
FB
1.25V
VDD
R2
Shut Down
EN
Q2
N MOS
Over Temp.
Detector
-
+
Loop Control Circuit
Q1
N MOS
R1
GND
DS9269-12 April 2011
www.richtek.com
3
RT9269
Absolute Maximum Ratings
Supply Voltage ---------------------------------------------------------------------------------------------------
−
0.3V to 7V
LX Pin Switch Voltage ------------------------------------------------------------------------------------------
−
0.3V to (V
DD
+0.8V)
Other I/O Pin Voltages ------------------------------------------------------------------------------------------
−
0.3V to (V
DD
+0.3V)
LX Pin Switch Current ------------------------------------------------------------------------------------------ 2.5A
EXT Pin Driver Current ------------------------------------------------------------------------------------------ 200mA
Power Dissipation, P
D
@ T
A
= 25°C
SOT-23-6 -----------------------------------------------------------------------------------------------------------
0.25W
Package Thermal Resistance
SOT-23-6,
θ
JA
----------------------------------------------------------------------------------------------------- 250°C/W
Operating Junction Temperature ------------------------------------------------------------------------------ 125°C
Storage Temperature Range -----------------------------------------------------------------------------------
−
65°C to +150°C
Electrical Characteristics
(V
IN
=3.3V, V
DD
set to 5V, Load Current = 0, T
A
= 25°C, unless otherwise specified)
Parameter
Start-UP Voltage
Operating V
DD
Range
No Load Current I (V
IN
)
Switch-off Current I (V
DD
)
Shutdown Current I (V
IN
)
Feedback Reference Voltage
Switching Rate
Maximum Duty
LX ON Resistance
Current Limit Setting
EXT ON Resistance to V
DD
EXT ON Resistance to GND
EN Pin Trip Level
Temperature Stability for V
REF
Thermal Shutdown
Thermal Shutdown Hysterises
Symbol
V
ST
V
DD
I
NO LOAD
I
SWITCH
I
OFF
V
REF
F
S
D
MAX
Test Conditions
I
L
= 1mA
V
DD
pin voltage
V
IN
= 3.3V, V
OUT
= 5V
V
IN
= 6V
EN Pin = 0V, V
IN
= 6V
Close Loop, VDD = 5V
V
DD
= 5V
V
DD
= 5V
V
DD
= 5V
Min
--
2
--
--
--
Typ
0.98
--
30
17
0.1
0.25
Max
1.05
6.5
--
--
1
Unit
V
V
μA
μA
μA
V
--
--
--
--
--
--
0.4
--
--
--
500
75
0.4
500
5
5
0.8
50
165
10
--
--
--
--
--
--
1.2
--
--
--
kHz
%
Ω
mA
Ω
Ω
V
ppm/
°C
°C
°C
I
LIMIT
V
DD
= 5V
V
DD
= 5V
V
DD
= 5V
V
DD
= 5V
T
S
T
SD
ΔT
SD
www.richtek.com
4
DS9269-12 April 2011
RT9269
Typical Operating Characteristics
Efficiency vs. Input Voltage
89
Efficiency vs. V
IN
85
4LEDs, L = 47uH
87
6LEDs, L = 33uH
84
Efficiency (%)
85
Efficiency(%)
83
I
OUT
= 20mA
83
I
OUT
= 20mA
82
81
80
79
81
I
OUT
= 15mA
I
OUT
= 15mA
79
2.5
3
3.5
4
4.5
5
5.5
6
3
3.5
4
4.5
5
5.5
6
Input Voltage (V)
V
IN
(V)
Frequency vs. V
DD
600
500
Efficiency vs. Input Voltage
100
I
OUT
= 20mA @V
IN
> 3.8V
90
Frequency(kHz)
A
400
300
200
100
Efficiency (%)
80
I
OUT
= 15mA
@V
IN
>
70
60
FB = GND, T
A
=25°C
0
0
1
2
3
4
5
6
Refer tp Application Circuit Figure 2
50
3
3.5
4
4.5
5
5.5
6
V
DD
(V)
Input Voltage (V)
VFB vs. Ambient Temperature
256
254
252
100
90
80
Efficiency vs. Output Current
Efficiency (%)
VFB (mV)
70
60
V
IN
= 2.7V
V
IN
= 4.2V
V
IN
= 3.6V
250
248
246
244
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80
50
40
30
20
0.1
1
10
100
Ambient Temperature
(
°C
)
DS9269-12 April 2011
Output Current (mA)
www.richtek.com
5
京公网安备 11010802033920号
EEWORLD
