LM3402 Reference Design - 4 InGaN White LEDs, 350 mA

Design Specifications

Inputs	Outputs #1
VinMin=15	Vout1=14
VinMax=16.5	Iout1=0.400

Design Resources

LM3402 Reference Design

Additional Resources

•	LM3402 Product Folder
•	LM3402EVAL Evaluation Board

Bill Of Materials

Part	Manufacturer	Part#	Attributes
Cb	Vishay	VJ0805Y103KXXAT	10n F
Cf	Vishay	VJ0805Y104KXXAT	100n F
Cin	TDK	C3225X7R1E225M	NumCaps=1, 2.2u F
Co	TDK	C3225X7R1E474M	0.47u F
D1	Central Semiconductor	CMSH1-40M	0.5 V
L1	TDK	SLF7045T-470MR75	47u H, 0.13 Ohms
Ron	Vishay	CRCW08051023F	102k Ohms
Rsns	Panasonic	ERJ6BQFR68V	0.68 Ohms
U1	National Semiconductor	LM3402

Design Description

This circuit is designed to drive an array of four series-connected InGaN WLEDs (typical Vf 13.8V total) at a continuous current of 400 mA from an input of 12VAC rectified to between 15V and 16.5V DC. Switching frequency is approximately 200 kHz to provide current control under near-dropout conditions.

Ripple current in the LED array is approximately +-10% of the average LED current.

Schematic

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