Microsemi

Integrated Products

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 1

Copyright

© 2001

Rev. 1.0d, 2005-03-14

LX1990

Dual Programmable LED Current Sink

TM

®

DESCRI PTI O N

The LX1990 is a dual output current

sink optimized for driving light emitting

diodes. This low cost bipolar IC enables

precise

current

regulation

in

LED

display

lighting

applications,

yet

requires far fewer parts than discrete

solutions. The LX1990 is supplied in a

micro-miniature 6 lead MLP package

featuring a 3 x 3 mm footprint, a profile

of less than 1mm, and much improved

thermal performance. Its two output sink

currents are accurately matched and

require only one resistor to program.

Program current is only 1% of the

output currents, and quiescent current is

low, providing a very high efficiency

driver for battery-powered displays.

The LX1990 is based on a current-

mirror

architecture

that

transfers

a

pin to each of two open-collector current

sinking outputs.

The output stages

multiply this reference current by 100 to

sink independently regulated currents up

to 30 mA.

Light output from LED’s is proportional

to average current through them; they can

easily produce a brightness range of 500:1.

However, color of emitted light is shifted by

current amplitude. Color shift at low light

levels can be reduced by driving the LED’s

with a constant peak current while dimming

with duty cycle control.

resistor with a PWM signal.

A 500:1

brightness

range

can

be

achieved

by

choosing 270 Hz as the PWM frequency (to

avoid optical beating with 50/60 Hz room

lights)

and

pulse

width

from

3.7

milliseconds to 7.4 microseconds.

The LX1990 features a shutdown mode

via the Enable pin.

In this mode the

LX1990 consumes less than 1

µA and holds

the two open collector output stages off.

This pin may also be used to pulse width

modulate output current. See applications

section for dimming details.

IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com

KEY FEATUR ES

• Programmable Sink Current

0.1 to 30mA x 2 Channels

• Replaces Discrete Transistor

Circuitry With A Single Package

• 300mV Maximum Current Sink

Dropout Voltage at 20mA

• 2.7 to 5.5V Power Supply Input

• Enable Input With <1µA Sleep

Current

• Amplitude and PWM Dimming

• Current rise and fall time may

be controlled to reduce EMI

A P PLI CATIONS

• Cell Phone Display Illumination

• PDA White LED Display

Lighting

• Automotive Display Illumination

• Digital Still Camera

• Camcorders

• Consumer Electronics Front

Panels

PRODUCT H I GHLIGHT

5V

LX1990

VDD

I

OUTB

GND

I

OUT A

ISET

R

SET

ENA

V

LO AD

ON/O FF

PACKAGE ORDER INFO

LM

Plastic MLP

6-Pin

°C)

RoHS Compliant / Pb-free Transition DC: 0452

-40 to 85

LX1990ILM

Note: Available in Tape & Reel. Append the letters “TR” to the part number. (i.e. LX1990ILM-TR)