Tiny Package, High Performance, Constant Current Switching Regulator W

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Tiny Package, High Performance, Constant Current Switching Regulator W

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RT9284A/B
Tiny Package, High Performance, Constant Current Switching Regulator White
RT9284A/B compact, high efficient high integration driver. Internal MOSFET support White LEDs backlighting camera flashing. Highly integration internal compensation network minimizes external component counts. Optimized operation frequency meet requirement small filters value operation current with high efficiency. Internal soft start function reduce inrush current. Tiny package type TSOT-23-5 TSOT-23-6 packages provide best solution space saving total cost.
Features
Operating Range 2.7V 5.5V Maximum Output Voltage Dimming with Zero-inrush Wide Frequency Range 100kHz Over Voltage Protection Output Current 100mA VOUT 12V. Zero Shutdown Supply Current Minimize External Component Small Filter Internal Soft Start RoHS Compliant 100% Lead (Pb)-Free
Ordering Information
RT9284 Package Type TSOT-23-5 TSOT-23-6 Operating Temperature Range Free with Commercial Standard Green (Halogen Free with Commercial Standard) Voltage Voltage 1.235V 0.25V
Note Richtek Pb-free Green products RoHS compliant compatible with current requirements IPC/JEDEC J-STD-020. Suitable SnPb Pb-free soldering processes. 100% matte (Sn) plating.
Applications
Camera Flash White Mobile Phone, Smart Phone Backlight Backlight Digital Still Camera Camcorder
Configurations
VIEW
TSOT-23-5
Marking Information
marking information, contact sales representative directly through Richtek distributor located your area, otherwise visit website detail.
TSOT-23-6 Note There pin1 indicator mark TSOT-23-6 type, will lower left when reading mark from left right.
DS9284A/B-05 August 2007
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RT9284A/B
Typical Application Circuit
4.7uH 22uH 2.7V 5.5V SS0520 1uF/16V ILED
RT9284
Dimming Control 100Hz-100kHz
Figure Application Driving Series WLEDs
4.7uH 22uH 2.7V 5.5V SS0520 1uF/25V ILED
RT9284
600k
Dimming Control 100Hz-100kHz
Figure Application Driving Series WLEDs
4.7uH 22uH 2.7V 5.5V SS0520 1uF/25V ILED
RT9284B
Dimming Control 100Hz-100kHz
0.25V
Figure Application Driving Series WLEDs
4.7uH 22uH 2.7V 5.5V SS0520
VOUT 130k 1uF/16V
RT9284A
1.235V
Figure Application Constant Output Voltage
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DS9284A/B-05 August 2007
RT9284A/B
Description
TSOT-23-5 TSOT-23-6 Switch Pin. Connect this inductor catch diode. Minimize track area reduce EMI. Ground Feedback Reference Voltage Pin. Series connect resistor between WLED ground current sense. Sense current feedback voltage current rating. Chip Enable (Active High). Voltage sensing input trigger function over voltage protection. Note that this high impedance. There should pull 100k resistor connected when control signal floating. Over Voltage Protection Pin. Voltage sensing input trigger function over voltage protection. Leave unconnected disable this function. Supply Input Voltage Pin. Bypass capacitor reduce input noise. Name Function
Function Block Diagram
1.2MHz Current Bias BandGap Protection Circuit UVLO Timer Buffer Soft Start VREF ibias VREF
750mA
Logic
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RT9284A/B
Absolute Maximum Ratings
(Note -0.3V -0.3V -0.3V -0.3V 0.455W 0.455W 220°C/W 220°C/W 260°C 150°C -65°C 150°C 200V Supply Input Voltage Input Voltage -OVP Voltage -The Other Pins -Power Dissipation, 25°C TSOT-23-5 -TSOT-23-6 -Package Thermal Resistance (Note TSOT-23-5, -TSOT-23-6, -Lead Temperature (Soldering, sec.) -Junction Temperature -Storage Temperature Range -ESD Susceptibility (Note (Human Body Mode) (Machine Mode)
Recommended Operating Conditions
(Note
Supply Input Voltage 2.7V 5.5V Junction Temperature Range -40°C 125°C Ambient Temperature Range -40°C 85°C
Electrical Characteristics
(VIN 3.7V, 25°C unless otherwise specified)
Parameter System Supply Input Operation voltage Range Under Voltage Lock Quiescent Current Supply Current Shut Down Current Line Regulation Oscillator Operation Frequency Maximum Duty Cycle Dimming Frequency Reference Voltage
Symbol
Test Condition
Units
1.5V, switch Switch 0.4V 3.0~4.3V
-2.2
1000
fOSC
-100k
RT9284A Feedback Voltage (Note RT9284B
1.173 0.237
1.235 0.25
1.296 0.263
continued
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RT9284A/B
Parameter MOSFET Resistance MOSFET Protection Threshold Sink Current Shut Down Voltage Enable Voltage 2,3,4 WLEDs application VOVP WLED application -1.5 -0.4 RDS(ON) -0.75 Symbol Test Condition Units
Note Stresses listed above "Absolute Maximum Ratings" cause permanent damage device. These stress ratings. Functional operation device these other conditions beyond those indicated operational sections specifications implied. Exposure absolute maximum rating conditions extended periods remain possibility affect device reliability. Note Devices sensitive. Handling precaution recommended. Note device guaranteed function outside operating conditions. Note measured natural convection 25°C effective thermal conductivity test board JEDEC 51-3 thermal measurement standard. Note Floating disable function.
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RT9284A/B
Typical Operating Characteristics
Enable Voltage Input Voltage
Shut Down Voltage Input Voltage
-45°C
Shut Down Voltage
Enable Voltage
-45°C
25°C
25°C 85°C
85°C
3.25 3.75 4.25 4.75 5.25
3.25 3.75
4.25 4.75
5.25
Input Voltage
Input Voltage
Efficiency Input Voltage
Current Input Voltage
4WLEDs,
21.5
ILED 20mA, 4.7H, 0.15
83.5
Current (mA)
3WLEDs
20.5 19.5 18.5
Efficiency
82.5
4WLEDs
81.5 80.5
3.25 3.75
4.25 4.75
5.25
Input Voltage
Input Voltage
Maximum Duty Cycle
(Rising/Falling) Temperature
Maximum Duty Cycle
Rising
Falling
3.25 3.75 4.25 4.75 5.25
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Temperature (°C)
DS9284A/B-05 August 2007
RT9284A/B
Switching Current Input Voltage
Switching Frequency Temperature
Switching Current (mA)
3.25 3.75 4.25 4.75
25°C
Switching Frequency (MHz)
-45°C
1.45 1.35 1.25 1.15 1.05
85°C
5.25
Input Voltage
Temperature (°C)
Feedback Voltage Temperature
252.2
Dimming Operation
4WLEDs, 3.7V, ILED 20mA,
Feedback Voltage (mV)
251.8 251.6 251.4 251.2 250.8 250.6
(5V/Div)
(50mA/Div)
(10mA/Div) 100Hz, Duty
Temperature (°C)
Time (2ms/Div)
Dimming Operation
4WLEDs, 3.7V, ILED 20mA,
Dimming Operation
4WLEDs, 3.7V, ILED 20mA,
(5V/Div) (5V/Div)
(100mA/Div)
(100mA/Div)
(10mA/Div)
(10mA/Div)
1kHz, Duty 10kHz, Duty
Time (400s/Div)
Time (40s/Div)
DS9284A/B-05 August 2007
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RT9284A/B
Dimming Operation
4WLEDs, 3.7V, ILED 20mA, (10V/Div) (5V/Div)
VOUT
(100mA/Div) (10mA/Div)
(500mA/Div)
100kHz, Duty
(20V/Div)
Time (4s/Div)
Time (25s/Div)
Inrush Current
4WLEDs, 3.0V, ILED 20mA, 4.7H (2V/Div)
Inrush Current
4WLEDs, 4.3V, ILED 20mA, 4.7H (2V/Div)
(2V/Div) (2V/Div) (5V/Div)
(5V/Div)
VOUT
(100mA/Div)
VOUT
(100mA/Div)
Time (500s/Div)
Time (500s/Div)
Normal Operation
(5V/Div) (2V/Div) (2V/Div) 4WLEDs, 3.0V ILED 20mA, (5V/Div)
Normal Operation
4WLEDs, 3.7V ILED 20mA,
VOUT
(10V/Div)
VOUT
(10V/Div)
(100mA/Div)
(100mA/Div)
Time (400ns/Div)
Time (400ns/Div)
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DS9284A/B-05 August 2007
RT9284A/B
Normal Operation
(5V/Div) (2V/Div) 4WLEDs, 4.3V ILED 20mA, (5V/Div) (2V/Div) 4WLEDs, 5.5V ILED 20mA,
Normal Operation
VOUT
(10V/Div)
VOUT
(10V/Div)
(100mA/Div)
(100mA/Div)
Time (400ns/Div)
Time (400ns/Div)
DS9284A/B-05 August 2007
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RT9284A/B
Application Information
Power Sequence RT9284A/B must take notice power sequence. power sequence RT9284A/B early than else RT9284A/B maybe fall into unknown state result RT9284A/B turn off.
2.7V 1.5V 0.4V
Using Voltage Using variable voltage adjust brightness popular method some applications. dimming control using voltage circuit shown Figure According Superposition Theorem, voltage increases, voltage contributed increases voltage drop decreases, i.e. current decreases. example, range from 2.8V, selection resistors Figure sets dimming control current from 20mA 0mA.
2.7V 5.5V 4.7uH 22uH SS0520
Figure Current Control RT9284A/B regulates current setting current sense resistor (R1) connecting feedback ground. shown Table RT9284A feedback voltage (VFB) 1.235V RT9284B feedback voltage (VFB) 0.25V. current (ILED) resistor order have accurate current, precision resistor preferred recommended). Table
Version RT9284A RT9284B Feedback Reference Voltage 1.235 0.25 Current Setting ILED ILED 1.235/R1 ILED 0.25/R1
1.5V 0.4V RT9284A
ILED
Dimming 2.8V
Figure Dimming Control Using Voltage RT9284A current calculated following equation. ILED (VDC
Using Filtered signal: Dimming Control Using Signal controlling brightness, RT9284A/B perform dimming control applying signal pin. internal soft start wide range dimming frequency from100 to100kHz eliminate inrush current audio noise when dimming. average current proportional signal duty cycle. magnitude signal should higher than maximum enable voltage pin, order dimming control perform correctly.
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Another common application using filtered signal adjustable voltage dimming control. filtered signal acts voltage regulate output current. recommended application circuit shown Figure this circuit, output ripple depends frequency signal. smaller output voltage ripple (<100mV), recommended frequency 2.8V signal should above 2kHz. frequency signal change duty cycle signal different output current. Figure shows relationship between current duty cycle.
DS9284A/B-05 August 2007
RT9284A/B
2.7V 5.5V 4.7uH 22uH SS0520
Capacitor Selection
ILED
RT9284A 1.5V 0.4V 2.8V Signal
Input output ceramic capacitors recommended RT9284A/B applications. better voltage filtering, ceramic capacitors with recommended. types suitable because their wider voltage temperature ranges. Diode Selection Schottky diode good choice RT9284A/B because forward voltage drop fast reverse recovery. Using Schottky diode better efficiency. highspeed rectification also good characteristic Schottky diode high switching frequency. Current rating diode must meet root mean square peak current output average current multiplication following
(RMS) (IOUT IPEAK
Figure Filtered Signal Dimming Control RT9284A current calculated following equation.
ILED
(VPWM Duty
diode' reverse breakdown voltage should larger than output voltage. SS0520 recommended Schottky diode rectifier. Layout Guide full plane without break. noise bypass-Short wide connection MLCC capacitor between Pin6 Pin2. Minimized node copper area reduce EMI. Minimized node copper area keep away from noise sources.
Current (mA)
Duty
Figure Inductor Selection recommended value inductor WLEDs applications 22H. Small size better efficiency major concerns portable device, such RT9284A/B used mobile phone. inductor should have core loss 1.2MHz better efficiency. avoid inductor saturation current rating should considered.
Figure Layer
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RT9284A/B
Figure Bottom Layer
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RT9284A/B
Outline Dimension
Symbol
Dimensions Millimeters 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
Dimensions Inches 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
TSOT-23-5 Surface Mount Package
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RT9284A/B
Symbol
Dimensions Millimeters 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
Dimensions Inches 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
TSOT-23-6 Surface Mount Package
Richtek Technology Corporation
Headquarter Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611
Richtek Technology Corporation
Taipei Office (Marketing) 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com
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DS9284A/B-05 August 2007

Tiny Package, High Performance, Constant Current Switching Regulator W

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