RT9284A15PJ6 [RICHTEK]
Tiny Package, High Performance, Constant Current Switching Regulator for White LED; 微型封装，高性能，恒流开关稳压器，用于白光LED
| 型号： | RT9284A15PJ6 |
| 厂家： | 
RICHTEK TECHNOLOGY CORPORATION |
| 描述： | Tiny Package, High Performance, Constant Current Switching Regulator for White LED |
| 文件： | 总14页 (文件大小：261K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
RT9284A/B
Tiny Package, High Performance, Constant Current
Switching Regulator for White LED
General Description
Features
z VIN Operating Range : 2.7V to 5.5V
z Maximum Output Voltage up to 20V
z Dimming with Zero-inrush and Wide Frequency
Range of 100 to 100kHz
The RT9284A/B is a compact, high efficient and high
integration LEDdriver. 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.
z Over Voltage Protection
z Output Current up to 100mA at VOUT = 12V.
z Zero Shutdown Supply Current
z Minimize the External Component
z Small LC Filter
z Internal Soft Start
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
Ordering Information
z Camera Flash White LED
z Mobile Phone, Smart Phone LED Backlight
z PDA LED Backlight
-
(
)
RT9284
Package Type
J5 : TSOT-23-5
J6 : TSOT-23-6
z Digital Still Camera
z Camcorder
Operating Temperature Range
P : Pb Free with Commercial Standard
G : Green (Halogen Free with
Commercial Standard)
Pin Configurations
OVP Voltage
15 : 15V
20 : 20V
TOP VIEW
VDD
EN
5
1
4
FB Voltage
A : 1.235V
B : 0.25V
2
3
Note :
FB
LX GND
Richtek Pb-free and Green products are :
`RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
TSOT-23-5
VDD OVP EN
`Suitable for use in SnPb or Pb-free soldering processes.
`100% matte tin (Sn) plating.
6
1
5
2
4
3
Marking Information
GND FB
LX
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.
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1
DS9284A/B-05 August 2007
RT9284A/B
Typical Application Circuit
D1
SS0520
L1
OVP
15V
4.7uH to 22uH
+
C1
1uF
C2
1uF/16V
I
LED
V
IN
2.7V to 5.5V
RT9284
VDD
6
4
2
1
5
LX
EN
Dimming
Control
100Hz-100kHz
OVP
FB
3
GND
R1
Figure 1. Application for Driving 3 Series WLEDs
D1
SS0520
L1
OVP
18V
4.7uH to 22uH
+
C1
1uF
C2
1uF/25V
I
LED
V
IN
2.7V to 5.5V
R2
600k
RT9284
VDD
6
4
2
1
5
LX
EN
Dimming
Control
100Hz-100kHz
OVP
FB
OVP 15V
3
GND
R1
Figure 2. Application for Driving 4 Series WLEDs
D1
SS0520
L1
OVP
20V
4.7uH to 22uH
+
C1
1uF
C2
1uF/25V
I
LED
V
IN
2.7V to 5.5V
RT9284B
VDD
6
4
2
1
5
LX
EN
Dimming
Control
100Hz-100kHz
OVP
FB
3
GND
V
= 0.25V
FB
R1
Figure 3. Application for Driving 5 Series WLEDs
D1
SS0520
L1
OVP
15V
4.7uH to 22uH
V
OUT
12V
+
C1
1uF
V
C2
1uF/16V
IN
R1
2.7V to 5.5V
130k
RT9284A
VDD
6
4
2
1
5
LX
EN
OVP
FB
3
GND
V
= 1.235V
FB
R2
15k
Figure 4. Application for Constant Output Voltage
DS9284A/B-05 August 2007
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2
RT9284A/B
Pin Description
Pin No.
Pin Name
Pin Function
TSOT-23-5 TSOT-23-6
Switch Pin. Connect this Pin to inductor and catch diode. Minimize the track
area to reduce EMI.
1
2
1
2
LX
GND
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.
3
4
3
4
FB
EN
Over Voltage Protection Pin. Voltage sensing input to trigger the function of
over voltage protection. Leave it unconnected to disable this function.
--
5
5
6
OVP
VDD
Supply Input Voltage Pin. Bypass 1uF capacitor to GND to reduce the input
noise.
Function Block Diagram
1.2MHz OSC
VDD
Current Bias
ibias
OCP
PWM
750mA
Logic
V
BandGap
REF
LX
Protection Circuit
OVP
+
-
OVP
EN
Buffer
UVLO
FB
+
-
V
REF
GND
Timer
5ms
Soft Start
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DS9284A/B-05 August 2007
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RT9284A/B
Absolute Maximum Ratings (Note 1)
z Supply Input Voltage------------------------------------------------------------------------------------------------------ −0.3V to 7V
z LX Input Voltage ----------------------------------------------------------------------------------------------------------- −0.3V to 22V
z OVP Voltage---------------------------------------------------------------------------------------------------------------- −0.3V to 22V
z The Other Pins ------------------------------------------------------------------------------------------------------------- −0.3V to 6V
z PowerDissipation, PD @ TA = 25°C
TSOT-23-5 ------------------------------------------------------------------------------------------------------------------- 0.455W
TSOT-23-6 ------------------------------------------------------------------------------------------------------------------- 0.455W
z Package Thermal Resistance (Note 4)
TSOT-23-5, θJA ------------------------------------------------------------------------------------------------------------- 220°C/W
TSOT-23-6, θJA ------------------------------------------------------------------------------------------------------------- 220°C/W
z Lead Temperature (Soldering, 10 sec.)------------------------------------------------------------------------------- 260°C
z Junction Temperature ----------------------------------------------------------------------------------------------------- 150°C
z Storage Temperature Range -------------------------------------------------------------------------------------------- −65°C to 150°C
z ESD Susceptibility (Note 2)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------- 2kV
MM (Machine Mode) ------------------------------------------------------------------------------------------------------ 200V
Recommended Operating Conditions (Note 3)
z Supply Input Voltage------------------------------------------------------------------------------------------------------ 2.7V to 5.5V
z Junction Temperature Range-------------------------------------------------------------------------------------------- −40°C to 125°C
z Ambient Temperature Range-------------------------------------------------------------------------------------------- −40°C to 85°C
Electrical Characteristics
(VIN = 3.7V, TA = 25°C unless otherwise specified)
Parameter
System Supply Input
Operation voltage Range
Under Voltage Lock Out
Quiescent Current
Supply Current
Symbol
Test Condition
Min
Typ
Max
Units
2.7
1.8
50
0.1
--
--
2.2
300
2
5.5
2.5
1000
3
V
V
V
V
DD
DD
FB = 1.5V, No switch
FB = 0V, Switch
uA
mA
uA
%
I
I
I
DD
DD
DD
Shut Down Current
Line Regulation
--
1
V
EN
V
IN
< 0.4V
--
3
--
: 3.0~4.3V
Oscillator
Operation Frequency
0.9
1.2
1.5
MHz
f
OSC
Maximum Duty Cycle
Dimming Frequency
Reference Voltage
85
--
--
--
%
100
100k
Hz
RT9284A
RT9284B
1.173
0.237
1.235
0.25
1.296
0.263
V
V
Feedback Voltage
(Note 5)
To be continued
DS9284A/B-05 August 2007
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4
RT9284A/B
Parameter
Symbol
Test Condition
Min
Typ
Max
Units
MOSFET
On Resistance of MOSFET
--
0.75
--
Ω
R
V
DS(ON)
Protection
for 2,3,4 WLEDs application
for 5 WLED application
14
19
--
15
20
5
16
21
--
V
V
OVP Threshold
OVP
OVP Sink Current
OCP
μA
mA
V
--
750
--
--
Shut Down Voltage
Enable Voltage
--
0.4
--
V
V
EN
EN
1.5
--
V
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. θJA is measured in the natural convection at TA = 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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DS9284A/B-05 August 2007
RT9284A/B
Typical Operating Characteristics
Enable Voltage vs. Input Voltage
Shut Down Voltage vs. Input Voltage
1.2
1.2
1.1
1
1.1
1.0
0.9
0.8
0.7
0.6
0.5
-45°C
-45°C
25°C
85°C
0.9
0.8
0.7
0.6
0.5
25°C
85°C
3
3.25 3.5 3.75
4
4.25 4.5 4.75
5
5.25 5.5
3
3.25 3.5 3.75
4
4.25 4.5 4.75
5
5.25 5.5
Input Voltage (V)
Input Voltage (V)
Efficiency vs. Input Voltage
LED Current vs. Input Voltage
22
21.5
21
84
4WLEDs, L = 10μH
ILED = 20mA, L = 4.7μH, DCR = 0.15Ω
83.5
83
3WLEDs
4WLEDs
20.5
20
82.5
82
19.5
19
81.5
81
18.5
18
80.5
3
3.25 3.5 3.75
4
4.25 4.5 4.75
5
5.25 5.5
3
3.2
3.4
3.6
3.8
4
4.2
4.4
Input Voltage (V)
Input Voltage (V)
Maximum Duty Cycle vs. VDD
POR (Rising/Falling) vs. Temperature
91
2.7
2.5
2.3
2.1
1.9
1.7
1.5
90
Rising
89
88
87
Falling
86
85
3
3.25 3.5 3.75
4
4.25 4.5 4.75
5
5.25 5.5
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90
Temperature (°C)
VDD (V)
DS9284A/B-05 August 2007
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6
RT9284A/B
Switching Current vs. Input Voltage
Switching Frequency vs. Temperature
2
1.8
1.6
1.4
1.2
1
1.5
1.45
1.4
-45°C
25°C
1.35
1.3
85°C
1.25
1.2
0.8
0.6
0.4
0.2
0
1.15
1.1
1.05
1
3
3.25 3.5 3.75
4
4.25 4.5 4.75
5
5.25 5.5
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90
(°C)
Input Voltage (V)
Temperature
Feedback Voltage vs. Temperature
Dimming Operation
252.2
252
4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH
(5V/Div)
EN
IIN
251.8
251.6
251.4
251.2
251
(50mA/Div)
(10mA/Div)
250.8
250.6
ILED
f = 100Hz, Duty = 50%
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90
Time (2ms/Div)
Temperature (°C)
Dimming Operation
Dimming Operation
4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH
4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH
EN
IIN
EN
IIN
(5V/Div)
(5V/Div)
(100mA/Div)
(100mA/Div)
(10mA/Div)
ILED
ILED
(10mA/Div)
f = 10kHz, Duty = 50%
f = 1kHz, Duty = 50%
Time (400μs/Div)
Time (40μs/Div)
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DS9284A/B-05 August 2007
7
RT9284A/B
OCP
Dimming Operation
L = 10μH
4WLEDs, VIN = 3.7V, ILED = 20mA, L = 10μH
(10V/Div)
EN
IIN
(5V/Div)
VOUT
ILX
(100mA/Div)
(10mA/Div)
(500mA/Div)
(20V/Div)
ILED
LX
f = 100kHz, Duty = 50%
Time (25μs/Div)
Time (4μs/Div)
Inrush Current
Inrush Current
4WLEDs, VIN = 3.0V, ILED = 20mA, L = 4.7μH
4WLEDs, VIN = 4.3V, ILED = 20mA, L = 4.7μH
(2V/Div)
(2V/Div)
(2V/Div)
EN
VIN
EN
VIN
(2V/Div)
(5V/Div)
(5V/Div)
VOUT
IIN
VOUT
IIN
(100mA/Div)
(100mA/Div)
Time (500μs/Div)
Time (500μs/Div)
Normal Operation
Normal Operation
(5V/Div)
(2V/Div)
(5V/Div)
4WLEDs, VIN = 3.0V
ILED = 20mA, L = 10μH
4WLEDs, VIN = 3.7V
ILED = 20mA, L = 10μH
(2V/Div)
VOUT
VIN
VOUT
VIN
(10V/Div)
(10V/Div)
LX
LX
IIN
IIN
(100mA/Div)
(100mA/Div)
Time (400ns/Div)
Time (400ns/Div)
DS9284A/B-05 August 2007
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8
RT9284A/B
Normal Operation
Normal Operation
(5V/Div)
(2V/Div)
(5V/Div)
4WLEDs, VIN = 5.5V
ILED = 20mA, L = 10μH
(2V/Div)
4WLEDs, VIN = 4.3V
ILED = 20mA, L = 10μH
VOUT
VIN
VOUT
VIN
(10V/Div)
(10V/Div)
LX
LX
IIN
IIN
(100mA/Div)
(100mA/Div)
Time (400ns/Div)
Time (400ns/Div)
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DS9284A/B-05 August 2007
RT9284A/B
Application Information
Power Sequence
b. Using a DC Voltage
The RT9284A/B must take notice of the power sequence.
The power sequence of RT9284A/B has to VDDearly than
EN or else the RT9284A/B maybe fall into the unknown
state to result in RT9284A/B turn off.
Using a variable DC voltage to adjust the brightness is a
popular method in some applications. The dimming control
using aDC voltage circuit is shown in Figure 6. According
to the Superposition Theorem, as the DC voltage
increases, the voltage contributed to VFB increases and
the voltage drop on R2 decreases, i.e. the LED current
decreases. For example, if the VDC range is from 0V to
2.8V, the selection of resistors in Figure 6 sets dimming
control of LED current from 20mA to 0mA.
V
> 2.7V
DD
V
DD
EN > 1.5V
EN < 0.4V
EN
D1
L1
4.7uH to 22uH SS0520
V
OUT
V
C1
IN
2.7V to 5.5V
Figure 5
I
LED
C2
RT9284A
LED Current Control
6
4
2
1
5
VDD
LX
OVP
FB
V
> 1.5V
EN
The RT9284A/B regulates the LED current by setting the
current sense resistor (R1) connecting to feedback and
ground. As shown in Table 1, the RT9284A feedback
voltage (VFB) is 1.235V and the RT9284B feedback voltage
(VFB) is 0.25V. The LED current (ILED) can be set by a
resistor R1. In order to have an accurate LED current, a
precision resistor is preferred (1% is recommended).
EN
V
< 0.4V
EN
R2
10k
3
GND
R3
R1
110
13k
V
Dimming
DC
0V to 2.8V
Figure 6. Dimming Control Using a DC Voltage for
RT9284A
Table 1
The LED current can be calculated by the following
equation.
Feedback Reference
LED Current
Setting I (A)
Version
Voltage V (V)
FB
LED
R2×(VDC − VFB
)
VFB
−
R3
RT9284A
RT9284B
1.235
0.25
I
= 1.235/R1
= 0.25/R1
LED
ILED
=
R1
I
LED
c. Using a Filtered PWM signal:
Another common application is using a filtered PWM
signal as an adjustableDC voltage for LEDdimming control.
A filtered PWM signal acts as the DC voltage to regulate
the output current. The recommended application circuit
is shown in the Figure 7. In this circuit, the output ripple
depends on the frequency of PWM signal. For smaller
output voltage ripple (<100mV), the recommended
frequency of 2.8V PWM signal should be above 2kHz. To
fix the frequency of PWM signal and change the duty
cycle of PWM signal can get different output current.
Figure 8. shows the relationship between LEDcurrent and
PWM duty cycle.
Dimming Control
a. Using a PWM Signal to EN Pin
For controlling the LED brightness, the RT9284A/B can
perform the dimming control by applying a PWM signal
to EN pin. The internal soft start and the wide range
dimming frequency from100 to100kHz can eliminate inrush
current and audio noise when dimming. The average LED
current is proportional to the PWM signal duty cycle. The
magnitude of the PWM signal should be higher than the
maximum enable voltage of EN pin, in order to let the
dimming control perform correctly.
DS9284A/B-05 August 2007
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10
RT9284A/B
D1
SS0520
L1
Capacitor Selection
4.7uH to 22uH
C1
V
IN
Input and output ceramic capacitors of 1μF are
recommended for RT9284A/B applications. For better
voltage filtering, ceramic capacitors with low ESR are
recommended. X5R and X7R types are suitable because
of their wider voltage and temperature ranges.
2.7V to 5.5V
I
LED
C2
RT9284A
6
1
5
VDD
LX
V
> 1.5V
EN
4
2
EN
OVP
FB
V
< 0.4V
EN
R2
10k
3
GND
Diode Selection
R3
10k
R1
110
Schottky diode is a good choice for RT9284A/B because
of its low forward voltage drop and fast reverse recovery.
R
3k
DC
C
DC
1uF
2.8V
0V
Using Schottky diode can get better efficiency. The high-
speed rectification is also a good characteristic of
Schottky diode for high switching frequency. Current rating
of the diode must meet the root mean square of the peak
current and output average current multiplication as
following :
PWM Signal
Figure 7. Filtered PWM Signal for LEDDimming Control
of RT9284A
The LED current can be calculated by the following
equation.
ID(RMS) ≈ (IOUT ×IPEAK
)
R2×(V
×Duty − V
)
PWM
FB
V
FB
−
R3 + R
DC
I
=
The diode’ s reverse breakdown voltage should be larger
than the output voltage. SS0520 is recommended Schottky
diode for rectifier.
LED
R1
20
18
16
14
12
10
8
Layout Guide
z AfullGNDplane without gap break.
z VCC to GND noise bypass–Short and wide connection
for the 1μF MLCC capacitor between Pin6 and Pin2.
z Minimized LX node copper area to reduce EMI.
z Minimized FB node copper area and keep far away from
noise sources.
6
4
2
0
0
10 20 30 40 50 60 70 80 90 100
PWM Duty (%)
Figure 8
Inductor Selection
The recommended value of inductor for 3 to 5 WLEDs
applications are 4.7 to 22μH. Small size and better
efficiency are the major concerns for portable device, such
as RT9284A/B used for mobile phone. The inductor should
have low core loss at 1.2MHz and low DCR for better
efficiency. To avoid inductor saturation current rating should
be considered.
Figure 9. Top Layer
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DS9284A/B-05 August 2007
RT9284A/B
Figure 10. Bottom Layer
DS9284A/B-05 August 2007
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12
RT9284A/B
Outline Dimension
H
D
L
B
C
A
b
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
A1
B
0.700
0.000
1.397
0.300
2.591
2.692
0.838
0.080
0.300
1.000
0.100
1.803
0.559
3.000
3.099
1.041
0.254
0.610
0.028
0.000
0.055
0.012
0.102
0.106
0.033
0.003
0.012
0.039
0.004
0.071
0.022
0.118
0.122
0.041
0.010
0.024
b
C
D
e
H
L
TSOT-23-5 Surface Mount Package
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DS9284A/B-05 August 2007
RT9284A/B
H
D
L
C
A
B
b
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
A1
B
0.700
0.000
1.397
0.300
2.591
2.692
0.838
0.080
0.300
1.000
0.100
1.803
0.559
3.000
3.099
1.041
0.254
0.610
0.028
0.000
0.055
0.012
0.102
0.106
0.033
0.003
0.012
0.039
0.004
0.071
0.022
0.118
0.122
0.041
0.010
0.024
b
C
D
e
H
L
TSOT-23-6 Surface Mount Package
Richtek Technology Corporation
Headquarter
Richtek Technology Corporation
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
Hsinchu, Taiwan, R.O.C.
8F, No. 137, Lane 235, Paochiao Road, Hsintien City
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)89191466 Fax: (8862)89191465
Email: marketing@richtek.com
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DS9284A/B-05 August 2007
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RICHTEK
RT9284B-15PJ6
Tiny Package, High Performance, Constant Current Switching Regulator for White LED
RICHTEK
RT9284B-15PJ6E
Tiny Package, High Performance, Constant Current Switching Regulator for White LED
RICHTEK
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