LM3401EVAL National Semiconductor, LM3401EVAL Datasheet

LM3401EVAL

Manufacturer Part Number

LM3401EVAL

Description

BOARD EVALUATION FOR LM3401

Manufacturer

National Semiconductor

Series

PowerWise®r

Datasheets

1.LM3401MMNOPB.pdf (18 pages)

2.LM3401EVAL.pdf (8 pages)

Specifications of LM3401EVAL

Current - Output / Channel

Outputs And Type

1, Non-Isolated

Features

Dimmable

Voltage - Input

4.5 ~ 35V

Utilized Ic / Part

LM3401

Kit Contents

Board

Svhc

No SVHC (15-Dec-2010)

Kit Features

Hysteretic Control For Speed And

Lead Free Status / RoHS Status

Not applicable / Not applicable

Voltage - Output

Lead Free Status / Rohs Status

Supplier Unconfirmed

Current page: 1 of 8
Download datasheet (892Kb)

LM3401 Demo Board

Introduction

The LM3401 is a switching buck regulator derived current

source designed to drive a series string of high power, high

brightness LEDs. The LM3401 controls an external P-FET,

allowing the user to select a power device for the desired level

of forward LED current. The LM3401 demo board can supply

continuous current as high as 1.0A from an input voltage

range of 4.5V to 35V. It is designed to operate at ambient

temperatures up to 75°C.

The LM3401 maintains constant current through any number

of series-connected LEDs as long as the input voltage is

greater than the combined forward voltage of the LED string.

The LM3401 demo board includes an input terminal for a dig-

ital dimming signal, which is compatible with PWM dimming

frequencies up to 10 kHz.

The complete demo board schematic is shown in Figure 1.

Typical waveforms and performance curves for the LM3401

demo board are shown in Figure 3 through Figure 10.

The standard Bill of Materials is shown in Table 2, with an

additional Bill of Materials for a high current application shown

average current

340 mA *

700 mA

LED

1.0A

TABLE 1. LED current setting resistors (* = default value)

FIGURE 1. Complete LM3401 Demo Board Schematic

300254

0.59Ω*

0.29Ω

0.20Ω

National Semiconductor

Application Note 1657

Allan Fisher

July 29, 2008

in Table 4. The pcb layout is shown in Figure 11 and Figure

12.

Powering Up

First, referring to Table 1, verify that the current setting resis-

tor, R1, matches the desired LED current, and that the current

limit resistor (R3) is set appropriately. The default values for

R1 and R3 set the average LED current at 340 mA with a

typical peak current limit threshold of 1.5A.

Next, connect the LED string to the terminals as shown in

Figure 2. Connect the input voltage supply to the VIN and

GND terminal posts. If dimming is being used, connect a dig-

ital PWM signal to the DIM post. When all connections and

polarities are verified, power can be applied. LED strings

should not be connected or disconnected from the output ter-

minals while the demo board is powered up.

The LM3401 demo board can be easily modified to drive a

variety of LEDs. Three current setting options are described

in Table 1. For more detailed design and device information,

refer to the LM3401 datasheet.

(typical current limit)

24.9 kΩ (1.5A)*

47 kΩ (2.8A)

68 kΩ (3.9A)

R1 power dissipation

142 mW

200 mW

68 mW

www.national.com

30025401

Related parts for LM3401EVAL

LM3401EVAL Summary of contents

Page 1

... FIGURE 1. Complete LM3401 Demo Board Schematic TABLE 1. LED current setting resistors (* = default value) LED average current 340 mA * 700 mA 1.0A © 2008 National Semiconductor Corporation National Semiconductor Application Note 1657 Allan Fisher July 29, 2008 in Table 4. The pcb layout is shown in Figure 11 and Figure 12. ...

Page 2

Connecting the LED Array The LM3401 demo board includes a female 6-pin SIP con- nector as well as two turret posts for the cathode and anode connections of the LED array. These are labeled “LED+” and “LED-“. Either connection can ...

Page 3

Typical Performance Characteristics Unless otherwise specified, the following conditions apply: Vin = 24V 25°C, LED = 2 x Osram Golden Dragon (Vf = 3.4V 350 mA) FIGURE 3. CS, SNS, and LED Current Waveforms FIGURE 4. ...

Page 4

FIGURE 9. Efficiency vs Input Voltage Driving 700 mA and 1A LEDs LED String Options The default LED current setting is 340 mA, typical of many 1W LEDs. To adjust this value, the current setting resistor, R1, can be changed ...

Page 5

TABLE 4. BOM for 3.5A Application (Vin = 5V to 20V) Ref. # Description IC1 LED Controller L1 5.2 µH, 5A, Inductor Q1 20V, 4A, 25 mΩ, PFET D1 30V, 4A, Schottky C1 25V, 10 µF, ceramic C2 50V, 33 ...

Page 6

FIGURE 12. Bottom Side PCB Layout 6 30025412 ...

Page 7

Notes 7 www.national.com ...

Page 8

... For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Amplifiers www.national.com/amplifiers Audio www.national.com/audio Clock Conditioners www.national.com/timing Data Converters www.national.com/adc Displays www.national.com/displays Ethernet www.national.com/ethernet Interface www.national.com/interface LVDS www.national.com/lvds Power Management www.national.com/power Switching Regulators www.national.com/switchers LDOs www ...

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