Richtek RT9284A-15PJ6, RT9284A-15PJ6E, RT9284A-20GJ6E, RT9284A-20PJ6, RT9284A-20PJ6E Schematic [ru]

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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 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

z V

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

z Over Voltage Protection

z Output Current up to 100mA at V

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

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

VDD EN

LX GND FB

TSOT-23-5

VDD OVP EN

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

LX GND FB

TSOT-23-6

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RT9284A/B

Typical Application Circuit

4.7uH to 22uH

SS0520

OVP

15V

2.7V to 5.5V

Dimming

Control

2.7V to 5.5V

Dimming

Control

100Hz-100kHz

1uF

RT9284

VDD

GND

OVP

Figure 1. Application for Driving 3 Series WLEDs

SS0520

OVP 15V

600k

100Hz-100kHz

1uF

4.7uH to 22uH

RT9284

VDD

GND

OVP

Figure 2. Application for Driving 4 Series WLEDs

OVP

18V

1uF/25V

1uF/16V

LED

2.7V to 5.5V

Dimming

Control

2.7V to 5.5V

SS0520

VFB = 0.25V

100Hz-100kHz

1uF

4.7uH to 22uH

RT9284B

VDD

GND

OVP

Figure 3. Application for Driving 5 Series WLEDs

4.7uH to 22uH

1uF

RT9284A

VDD

GND

OVP

SS0520

OVP

15V

OVP

20V

1uF/25V

130k

R2 15k

1uF/16V

= 1.235V

LED

12V

OUT

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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

Current Bias

BandGap

Protection Circuit

OVP

UVLO

Timer

5ms

ibias

REF

1.2MHz OSC

OCP

750mA

Soft Start

PWM Logic

Buffer

REF

GND

DS9284A/B-07 April 2011

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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

TSOT-23-5 ----------------------------------------------------------------------------------------------------------------- 0.455W TSOT-23-6 ----------------------------------------------------------------------------------------------------------------- 0.455W

z Package Thermal Resistance (Note 2)

TSOT-23-5, θJA------------------------------------------------------------------------------------------------------------ 220°C/W TSOT-23-6, θJA------------------------------------------------------------------------------------------------------------ 220°C/W

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

= 25°C

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

= 3.7V, T

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)

Parameter Symbol Test Conditions Min Typ Max Unit

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

: 3.0~4.3V

-- -- 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)

RT9284B 0.237 0.25 0.263

T o be continued

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DS9284A/B-07 April 2011

MOSFET

RT9284A/B

Parameter Symbol Test Condition Min Typ Max Unit

On Resistance of MOSFET

DS(ON)

-- 0.75 --

Protection

for 2,3,4 WLEDs application 14 15 16

OVP Threshold

OVP

for 5 WLED application 19 20 21

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

JEDEC 51-3 thermal measurement standard.

1.5 -- -- V

-- -- 0.4 V

= 25°C on a low effective thermal conductivity test board of

DS9284A/B-07 April 2011

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