LM3485LED EVAL National Semiconductor, LM3485LED EVAL Datasheet

LM3485LED EVAL

Manufacturer Part Number

LM3485LED EVAL

Description

BOARD EVALUATION LM3485LED

Manufacturer

National Semiconductor

Datasheets

1.LM3485MMNOPB.pdf (16 pages)

2.LM3485LED_EVAL.pdf (4 pages)

Specifications of LM3485LED EVAL

Current - Output / Channel

1.4A

Outputs And Type

1, Non-Isolated

Voltage - Output

30V

Features

Dimmable

Voltage - Input

5 ~ 30V

Utilized Ic / Part

LM3485

Lead Free Status / RoHS Status

Not applicable / Not applicable

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LM3485 LED Demo Board

Introduction

The LM3485 LED driver board is a buck regulator derived

controlled current source designed to drive high power, high

brightness LEDs (HBLEDs) such as the Luxeon

dissipations of 1W to 5W. The board can accept an input

voltage ranging from 5V to 30V and can control the output

current delivered to series and/or parallel arrays of HBLEDs

as long as the forward voltage of all LEDs in series is less

than (0.9 x VIN). The accuracy of the output current is

Setting the LED Current

The forward current IF delivered to the LED array is set by

the program jumper, P2. If no jumper is installed, the

LM3485 will default to the lowest current setting, 350 mA.

Installing a jumper as shown in Figure 1 will change the

current regulation point to 700 mA, 100 mA, or 1400 mA,

respectively.

FIGURE 1. Current Settings of P2

AN201577

20157701

™

Emitter at

10%.

National Semiconductor

Application Note 1392

Chris Richardson

June 2006

PWM Dimming

Diode D2 provides an input for a pulse width modulation

signal for dimming of the LED array. In order to fully enable

and disable the LM3485 the PWM signal should have a

maximum logic low level of 1.0V, a minimum logic high level

of 2.0V, and minimum low and high periods of 40 µs. For

example, at 100Hz, the minimum and maximum duty cycles

to which the LM3485 can respond are 0.4% and 99.6%,

respectively. At 1 kHz, the minimum and maximum duty

cycles are 4% and 96%, respectively.

The logic of the PWM is inverted, hence the LM3485 will

deliver regulated output current when the voltage at the

PWM IN terminal is low, and the current output is disabled

when the voltage at the PWM IN terminal is high. Connecting

a constant logic high to the PWM IN will disable the output.

Output Open Circuit

With PWM IN floating or connected to logic low, the LM3485

will begin to operate as soon as is has an input of at least 5V.

In the case that the input is powered but no LED array is

connected the output voltage will rise to equal the input

voltage. The output of the circuit is rated to 30V and will not

suffer damage, however care should be taken not to connect

an LED array if the output voltage is higher than the target

forward voltage of the LED array in steady state.

www.national.com

Related parts for LM3485LED EVAL

LM3485LED EVAL Summary of contents

Page 1

... LM3485 will default to the lowest current setting, 350 mA. Installing a jumper as shown in Figure 1 will change the current regulation point to 700 mA, 100 mA, or 1400 mA, respectively. FIGURE 1. Current Settings of P2 © 2006 National Semiconductor Corporation National Semiconductor Application Note 1392 Chris Richardson June 2006 ...

Page 2

Typical Application Circuit www.national.com FIGURE 2. Circuit Schematic 2 20157702 ...

Page 3

ID Part Number U1 LM3485 U2 LM321 L1 SLF7045T-6R8M1R7 Q1 Si3483DV D1 SS24 D2 MBR0520 Cff VJ0805Y102KXXAT Cf C2012X7R1H104M Ccl VJ0805A101KXXAT Cin, Co C3216X7R1H105M Rff CRCW08051002F Resr CRCW08051R00F Rcl CRCW08052552F Rset CRCW1206R500J Ri CRCW08051002F R350 CRCW08056192F R700 CRCW08054422F R1 CRCW08051962F ...

Page 4

... BANNED SUBSTANCE COMPLIANCE National Semiconductor follows the provisions of the Product Stewardship Guide for Customers (CSP-9-111C2) and Banned Substances and Materials of Interest Specification (CSP-9-111S2) for regulatory environmental compliance. Details may be found at: www.national.com/quality/green. ...

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