LM3405XEVAL National Semiconductor, LM3405XEVAL Datasheet

LM3405XEVAL

Manufacturer Part Number

LM3405XEVAL

Description

BOARD EVALUATION LM3405X

Manufacturer

National Semiconductor

Series

PowerWise®r

Datasheets

1.LM3405XMKNOPB.pdf (20 pages)

2.LM3405XEVAL.pdf (8 pages)

3.LM3405XEVAL.pdf (20 pages)

Specifications of LM3405XEVAL

Current - Output / Channel

Outputs And Type

1, Non-Isolated

Voltage - Output

0.2 ~ 13.5 V

Features

Dimmable

Voltage - Input

3 ~ 15V

Utilized Ic / Part

LM3405

Kit Contents

Board, Datasheet

Svhc

No SVHC (15-Dec-2010)

Kit Features

Cycle-by-Cycle Current Limit,

Rohs Compliant

Lead Free Status / RoHS Status

Contains lead / RoHS non-compliant

Current page: 1 of 8
Download datasheet (476Kb)

LM3405 Demo Board

Introduction

The LM3405 demo board is configured to drive a series string

of high power, high brightness LEDs at a forward current of

1A using the LM3405 constant current buck regulator. The

board can accept a full input operating range of 3V to 15V.

The converter output voltage adjusts as needed to maintain

a constant current through the LED array. The LM3405 is a

step-down regulator with an output voltage range extending

from a V

determined by the maximum duty cycle (typically 94%). It can

drive up to 3 LEDs in series at 1A forward current, with the

single LED forward voltage of approximately 3.7V (Typical of

white, blue, and green LEDs using InGaN technology).

As shown in the demo board schematic circuit in Figure 1, the

board is configured with the boost voltage derived from V

through a shunt zener (D3). This will ensure that the gate drive

voltage V

to 5.5V when V

voltages (3V to 5V) being used, the boost diode (D2) can be

directly connected to V

to obtain sufficient gate drive voltage for best performance.

Table 1 lists the bill of materials of this demo board. The mea-

sured performance characteristics and layout of this board

are also included below. Additional Circuit Configuration

Schematics section illustrates other possible circuit configu-

rations of this board to accommodate various input and output

requirements as discussed in the LM3405 datasheet.

Connecting to LED Array

The LM3405 Demo Board includes a female 6-position SIP

connector P1 as well as two standard 72mil turret connectors

O(MIN)

BOOST

of 205mV (the reference voltage) to a V

- V

varies from 5V to 15V. In cases of low input

falls in the recommended range of 2.5V

(R3 short, C4 and D3 not installed)

FIGURE 1. LM3405 Demo Board Schematic

300100

O(MAX)

National Semiconductor

Application Note 1590

Alex Gao

March 2007

for the cathode and anode connections of the LED array. Solid

18 or 20 gauge wire with about 1cm of insulation stripped

away makes a convenient, solderless connection to P1.

Setting the LED Current

The default forward current I

1.0A. To adjust this value the current setting resistor R1 can

be changed according to the following equation:

The feedback voltage V

The resistor R1 should be rated to handle the power dissipa-

tion of the LED current. R1 should be less than approximately

1Ω, to ensure that the LED current is kept above 200mA. If

average LED currents of less than 200mA are desired, the

EN/DIM pin should be used for PWM dimming.

PWM Dimming

The default connection of the PWM terminal is tied to V

through a 100kΩ resistor (R2) to enable the chip, which allows

the set current to flow through the LEDs continuously. This

PWM terminal can also be connected separately to a periodic

pulse signal at different frequencies and/or duty cycle for

PWM dimming. A typical LED current waveform in PWM dim-

ming mode is shown in Figure 2. Figure 3 shows the average

LED current versus duty cycle of PWM dimming signal for

various frequencies. Due to an approximately 100µs delay

between the dimming signal and LED current, the dimming

ratio reduces dramatically if the applied PWM dimming fre-

quency is greater than 5kHz.

= V

is regulated at 0.205V typically.

delivered to the LED array is

/ R1

www.national.com

30010001

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LM3405XEVAL Summary of contents

Page 1

... LM3405 datasheet. Connecting to LED Array The LM3405 Demo Board includes a female 6-position SIP connector P1 as well as two standard 72mil turret connectors © 2007 National Semiconductor Corporation National Semiconductor Application Note 1590 Alex Gao March 2007 for the cathode and anode connections of the LED array ...

Page 2

... Part Value SLF6028T-6R8M1R5-PF GRM31CR61E106KA12L C1206C105K3RACTU 0805YC103KAT2A GRM219R71C104KA01D GRM216R61E105KA12D Not installed WSL2010R2000FEA CRCW0805100KFKEA CRCW08051K00FKEA 2 PWM Dimming Signal at PWM Terminal Part Number Manufacturer LM3405 National Semiconductor TDK Murata Kemet AVX Murata Murata MBRA130LT3G ON Semiconductor BAT54WS-TP Micro Commercial Co. BZX84C5V1 Fairchild Semiconductor Vishay Vishay Vishay ...

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LM3405XEVAL National Semiconductor, LM3405XEVAL Datasheet

LM3405XEVAL

Specifications of LM3405XEVAL

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LM3405XEVAL Summary of contents

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