Document
LA8303
300KHz, 2A/23V Step-Down LED Driver
General Description
LA8303 is a voltage mode, step-down LED driver that is designed to meet maximum 2A constant current for high power LED application, and utilizes PWM control scheme that switches with 300KHz fixed frequency. The input voltage range of LA8303 is from 3.6V to 23V. It is suitable for series-parallel 1W, 3W, or 5W high power LED application due to the high operation voltage and output capability. At 12VIN, this device can drive up to 15pcs (3S-5P) 1W LEDs. The 0.21V low feedback voltage can reduce the power dissipation of the constant current setting resistor, and improve the conversion efficiency. This device provides excellent regulation
Features
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Up to 96% Efficiency 0.21V Low Feedback Voltage 3.6V to 23V Input Voltage Range Driving up to 15 LEDs (1W 3S-5P) at 12VIN 300KHz Oscillation Frequency Continuous 2A Output Capability 100% Duty Cycle 3mA Low Supply Current 1uA Low Shutdown Current PWM or Analog Dimming Control Built-in Low RDS(ON) Power MOSFET No External Compensation Required Adjustable Current Limit Short Circuit and Thermal Protection SOP-8 Package Meet RoHS Standard
during line or load transient. Other features of external ON/OFF control, current limit, thermal shutdown protection, and short circuit protection are also included. It can also operate with a maximum duty cycle of 100% for use in low drop-out conditions. The package is available in standard SOP-8.
Applications
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High Power LED Driver Backlight Applications General Lighting Solutions Constant Current Source
Ordering Information
LA8303 1 2 3 4 1 (Package Type) => J: SOP
Marking Information
LA8303JG 1234
2 (Number of Pins) => G: 8pin 3 (Output Voltage) => Blank: Adjustable 4 (Special Feature) => Blank: N/A Available Part Number LA8303JG
1 2 (Date Code) For date code rule, please contact our sales representative directly. 3 4 (Internal Code)
LA8303-C01
-1-
Jun. 11, 2009
LA8303
Typical Application
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LED Light Bar Application ; Maximum 2A LED Current
DC5V~23V 3.3K
3
68uH or more OCSET SW
5,6
LA8303
2
EN
2A SBD 3K
4
IN GND
7,8
FB
1
LED Light Bar 220nF RFB=0.21V/ILED
CIN
4.7uF 25V
0.1uF 25V
* CIN up to 10uF or more for Hot-Plugging application * Power Dissipation on RFB is 0.21VxILED
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High Power LED Application with Dimming Control
DC5V~23V 3.3K
3
33uH OCSET SW
5,6
LA8303
2
EN
2A SBD Optional
4
IN GND
7,8
FB
1
5K RFB=0.21V/ILED
100uF
10uF 25V
0.1uF 25V 120K
PWM Dimming 10K 0.1uF or
DC 0V~5V
Analog Dimming
* ILED_MIN / ILED_MAX=0.05
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MR-16 1Wx3 Application ; 350mA Constant LED Current
47uH VIN 1A SBD 1A SBD
2
2.4K
3
OCSET
SW
5,6
LA8303
EN
1A SBD 300R
4
IN GND
7,8
FB
1
1A SBD VIN
1A SBD
CIN 25V
0.1uF 25V
220nF 33R 0.6R 0805
* Recommended CIN : 330uF or more
LA8303-C01
-2-
Jun. 11, 2009
LA8303
Efficiency Curve
ILED=350mA
1 LED 4 LEDs 100% 2 LEDs 5 LEDs 3 LEDs 100%
ILED=700mA
1 LED 4 LEDs 2 LEDs 5 LEDs 3 LEDs
90% Efficiency (%)
90% Efficiency (%) 4 6 8 10 12 14 16 18 Input Voltage (V) 20 22 24
80%
80%
70%
70%
60%
60%
50%
50% 4 6 8 10 12 14 16 18 Input Voltage (V) 20 22 24
ILED=1A
1 LED 4 LEDs 100% 2 LEDs 5 LEDs 3 LEDs 100% 1 LED 4 LEDs
ILED=2A
2 LEDs 5 LEDs 3 LEDs
90%
90%
Efficiency (%)
80%
Efficiency (%) 4 6 8 10 12 14 16 18 Input Voltage (V) 20 22 24
80%
70%
70%
60%
60%
50%
50% 4 6 8 10 12 14 16 18 Input Voltage (V) 20 22 24
LA8303-C01
-3-
Jun. 11, 2009
LA8303
Functional Block Diagram
SW
300KHz OSC 0.21V Reference Voltage
IN
PWM-Switched Control Circuit Thermal Shutdown VON/OFF 90uA + -
FB
GND
EN
OCSET
Pin Configurations
FB EN OCSET IN GND
SOP-8
GND SW SW
Pin No. 1
Name FB
Description
This pin senses the feedback voltage to set the LED current. Connect this pin to a resistor (RFB) to set constant LED current by the following formula: ILED=0.21V/RFB This pin allows an external control signal to turn-on/off this device. Float this pin or force it below 0.8V to turn-off this device, force it above 2V to turn-on this device. If this feature is not needed, connect this pin to IN directly. Add an external resistor from this pin to IN to set current Limit. The input pin of the step-down converter. A suitably large capacitor must be connected from this pin to ground to bypass noise on the input of the IC. The output pin of the step-down converter. This pin is the switching node that supplies power to the output. Connect a LC filter from this pin to the output load and a rectifier diode to the ground. The ground pin of the step-down converter. Connect this pin to the circuit ground.
2 3 4
EN OCSET IN
5,6 7,8
LA8303-C01
SW GND
-4-
Jun. 11, 2009
LA8303
Absolute Maximum Ratings
Parameter
Input Voltage SW Pin Voltage Range FB Pin Voltage Range EN Pin Voltage Range Storage Temperature Range Junction Temperature Lead Soldering Temperature (10 sec)
Rating
25V -0.5V ~ VIN+0.5V -0.3V ~ VIN -0.3V ~ VIN+0.3V -65°C ~ 150°C 150°C 300°C
These are stress .