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 ba cklighting a nd ca mera fla shing.
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 ca n reduce the inrush
current. Tiny pa ckage type of TSOT-23-5 a nd TSOT -23-6
pack ages provide the best solution for PCB spa ce saving
and total BOM cost.
Ordering Information
-
RT9284
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.
( )
Package Type
J5 : TSOT-23- 5
J6 : TSOT-23- 6
Lead Plating System
P : Pb Free
G : Green (Halogen Free and Pb Free)
OVP Voltage
15 : 15V
20 : 20V
FB Voltage
A : 1.235V
B : 0.25V
Features
zz
z V
Operating Range : 2.7V to 5.5V
zz
IN
zz
z Maximum Output Voltage up to 20V
zz
zz
z Dimming with Zero-inrush and Wide Frequency
zz
Range of 100 to 100kHz
zz
z Over Voltage Protection
zz
zz
z Output Current up to 100mA at V
zz
zz
z Zero Shutdown Supply Current
zz
zz
z Minimize the External Component
zz
zz
z Small LC Filter
zz
zz
z Internal Soft Start
zz
zz
z RoHS Compliant and 100% Lead (Pb)-Free
zz
OUT
: 12V
Applications
z Camera Fla sh White LED
z Mobile Phone, Smart Phone LED Ba cklight
z PDA LED Ba cklight
z Digital Still Camera
z Ca mcorder
Pin Configurations
TOP VIEW
VDDEN
5
LX GND FB
TSOT-23-5
VDD OVP EN
4
23
4
56
Marking Information
For marking information, conta ct our sales representative
directly or through a Richtek distributor located in your
area.
DS9284A/B-07 April 2011
23
LX GND FB
TSOT-23-6
www.richtek.com
1
RT9284A/B
Typical Application Circuit
L1
4.7uH to 22uH
D1
SS0520
OVP
15V
V
IN
2.7V to 5.5V
Dimming
Control
V
IN
2.7V to 5.5V
Dimming
Control
+
100Hz-100kHz
C1
1uF
RT9284
6
VDD
4
EN
2
GND
LX
OVP
FB
1
5
3
Figure 1. Application for Driving 3 Series WLEDs
SS0520
1
5
OVP 15V
3
D1
600k
+
100Hz-100kHz
C1
1uF
4.7uH to 22uH
RT9284
6
VDD
4
EN
2
GND
L1
LX
OVP
FB
Figure 2. Application for Driving 4 Series WLEDs
R2
OVP
18V
1uF/25V
C2
1uF/16V
C2
R1
R1
I
I
LED
LED
V
IN
2.7V to 5.5V
Dimming
Control
V
IN
2.7V to 5.5V
D1
SS0520
VFB = 0.25V
+
100Hz-100kHz
C1
1uF
4.7uH to 22uH
RT9284B
6
VDD
4
EN
2
GND
L1
LX
OVP
FB
1
5
3
Figure 3. Application for Driving 5 Series WLEDs
L1
4.7uH to 22uH
+
C1
1uF
6
4
2
RT9284A
VDD
EN
GND
LX
OVP
FB
D1
SS0520
1
5
3
OVP
15V
OVP
20V
C2
1uF/25V
R1
130k
V
FB
R2
15k
C2
1uF/16V
= 1.235V
R1
I
LED
V
12V
OUT
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2
Figure 4. Application f or Constant Output V oltage
DS9284A/B-07 April 2011
Pin Description
RT9284A/B
Pin No.
Pin Name Pin Function
TSOT-23-5 TSOT-23-6
1 1 LX
Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track
area to reduce EMI.
2 2 GND Ground Pin
Feedback Reference Voltage Pin. Series connect a resistor between WLED
3 3 FB
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
4 4 EN
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.
-- 5 OVP
5 6 VDD
Over Voltage Protection Pin. Voltage sensing input to trigger the function of
over voltage protecti on. Leave it unconnecte d to disable this function.
Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input
noise.
Function Block Diagram
VDD
OVP
EN
Current Bias
BandGap
Protection Circuit
OVP
UVLO
Timer
5ms
ibias
V
REF
1.2MHz OSC
OCP
750mA
Soft Start
PWM
Logic
LX
+
-
Buffer
+
-
FB
V
REF
GND
DS9284A/B-07 April 2011
www.richtek.com
3
RT9284A/B
Absolute Maximum Ratings (Note 1)
z Supply Input V oltage ---------------------------------------------------------------------------------------------------- −0.3V to 7V
z LX Input V oltage---------------------------------------------------------------------------------------------------------- −0.3V to 22V
z OVP Voltage -------------------------------------------------------------------------------------------------------------- −0.3V to 22V
z The Other Pins ----------------------------------------------------------------------------------------------------------- −0.3V to 6V
z Power Dissipation, P
z Lead T emperature (Soldering, 10 sec.) ----------------------------------------------------------------------------- 260°C
z Junction T emperature --------------------------------------------------------------------------------------------------- 150°C
z Storage T emperature Range------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 3)
HBM (Human Body Mode)--------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ---------------------------------------------------------------------------------------------------- 200V
@ T
D
= 25°C
A
Recommended Operating Conditions (Note 4)
z Supply Input V oltage ---------------------------------------------------------------------------------------------------- 2.7V to 5.5V
z Junction T emperature Range ------------------------------------------------------------------------------------------ −40°C to 125°C
z Ambient T emperature Range ------------------------------------------------------------------------------------------ −40°C to 85°C
Electrical Characteristics
(V
= 3.7V, T
IN
System Supply Input
Operation voltage Range
Under Voltage Lock Out
Quiescent Current
Supply Current
Shut Do wn Current
Line Regulation
Oscillator
Operation Frequency
= 25°C unless otherwise specified)
A
Parameter Symbol Test Conditions Min Typ Max Unit
V
DD
V
DD
I
DD
I
DD
V
I
DD
f
OSC
2.7 -- 5.5 V
1.8 2.2 2.5 V
FB = 1.5V, No switch 50 300 1000 uA
FB = 0V, Switch 0.1 2 3 mA
< 0.4V
EN
V
: 3.0~4.3V
IN
-- -- 1 uA
-- 3 -- %
0.9 1.2 1.5 MHz
Maxi mum Du ty Cyc le 85 - - -- %
Dimming Frequency 100 -- 100k Hz
Reference Voltage
RT9284A 1.173 1.235 1.296
Feedback Voltage (Note 5)
V
RT9284B 0.237 0.25 0.263
T o be continued
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4
DS9284A/B-07 April 2011
MOSFET
RT9284A/B
Parameter Symbol Test Condition Min Typ Max Unit
On Resistance of MOSFET
R
DS(ON)
-- 0.75 --
Ω
Protection
for 2,3,4 WLEDs application 14 15 16
OVP Threshold
V
OVP
for 5 WLED application 19 20 21
V
OVP Sink Cur rent -- 5 -- μA
OCP -- 750 -- mA
Shut Down Voltage
Enable Voltage
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. θ
Note 3. Devices are ESD sensitive. Handling precaution recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Note 5. Floating the OVP pin to disable OVP function.
is measured in the natural convection at T
JA
JEDEC 51-3 thermal measurement standard.
V
EN
V
EN
1.5 -- -- V
-- -- 0.4 V
= 25°C on a low effective thermal conductivity test board of
A
DS9284A/B-07 April 2011
www.richtek.com
5
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