LM3402 Reference Design - 1-2 InGaN LEDs, 335 mA

Design Specifications

Inputs	Outputs #1
VinMin=9	Vout1=3.5
VinMax=16	Iout1=0.335

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	C3225X7R1H225M	NumCaps=1, 2.2u F
Co	Vishay	VJ0805Y564KXXAT	560n F
D1	Central Semiconductor	CMSH1-40M	0.5 V
L1	TDK	SLF7045T-470MR75	47u H, 0.13 Ohms
Ron	Vishay	CRCW08056982F	69.8k Ohms
Rsns	Panasonic	ERJ6BQFR68V	0.68 Ohms
U1	National Semiconductor	LM3402

Design Description

These circuits are designed to drive a string of 1 or 2 InGaN LEDs at a forward current of 335 mA with a peak-to-peak ripple current of 100 mA or less. The input is 9V to 16V, with LED current and switching frequency (400 kHz) centered at Vin = 12.8V.

This circuit is rated to withstand input voltage surges up to 25V. This can be increased to 42V by changing Cin and D1 to ratings of 50V or more.

Schematic

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