LM3402 Reference Design - 3 AlInGaP Red/Amber LEDs, 350 mA

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Design Specifications

Inputs	Outputs #1
VinMin=10	Vout1=7.7
VinMax=42	Iout1=0.350

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	C3225X7R1H335M	NumCaps=1, 3.3u F
D1	Central Semiconductor	CMSH1-60M	0.5 V
L1	TDK	SLF7045T-680MR75-1PF	68u H, 0.27 Ohms
Ron	Vishay	CRCW08058252F	82.5k Ohms
Rsns	Panasonic	ERJ6BQFR62V	0.62 Ohms
U1	National Semiconductor	LM3402

Design Description

This circuit has been designed to drive a string of three AlInGaP red or amber LEDs (total Vo = 7.7V) at a forward current of 350 mA +-10% mA with a peak-to-peak ripple current of 140 mA or less. The input is 10V to 42V, with LED current and switching frequency (700 kHz) centered at Vin = 24V.

In expectation of fast PWM dimming requirements there is no output capacitor used in this design.

Schematic

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