LM3401-MR16DEMO/NOPB National Semiconductor, LM3401-MR16DEMO/NOPB Datasheet

LM3401-MR16DEMO/NOPB

Manufacturer Part Number

LM3401-MR16DEMO/NOPB

Description

BOARD DEMO LM3401

Manufacturer

National Semiconductor

Series

PowerWise®r

Datasheets

1.LM3401EVAL.pdf (8 pages)

2.LM3401-MR16DEMONOPB.pdf (18 pages)

Specifications of LM3401-MR16DEMO/NOPB

Current - Output / Channel

1.5A

Outputs And Type

1, Non-Isolated

Voltage - Output

Features

Voltage - Input

4.5 ~ 35 V

Utilized Ic / Part

LM3401

Lead Free Status / Rohs Status

Lead free / RoHS Compliant

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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 LM3401-MR16DEMO/NOPB

LM3401-MR16DEMO/NOPB Summary of contents

Page 1

... 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 kHz. ...

Page 2

... Open Circuit/Short Circuit 30025402 If the LED array is disconnected or fails open, the LM3401 will operate at 100% duty cycle. The output voltage (at LED+) and CS node will rise to equal the input voltage; the circuit is rated to 40V and will not suffer damage. However, care should be ...

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

... Luxeon V Star 1 Luxeon K2 Emitter The LM3401 can also drive LED currents in excess of 1A. For these applications a larger pad is provided for a higher current PFET. An example BOM for a typical 3.5A application is shown in Table 4. The switching frequency, ripple current, and current limit values will depend on the number and type of www ...

Page 5

... PFET D1 30V, 4A, Schottky C1 25V, 10 µF, ceramic C2 50V, 33 µF, electrolytic C3 25V, 220 pF, ceramic 0.0576Ω, 1 4.7 kΩ kΩ,1% PCB Layout Part Number LM3401 MSS1038-522NL Si3493BDV SSB43L C3225X5R1E106K EEEHA1H330XP - WSL2512R0576F - - FIGURE 11. Top Side PCB Layout 5 Size Vendor MSOP-8 NSC 10.2 x 10.4 ...

Page 6

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

Page 7

Notes 7 www.national.com ...

Page 8

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