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MAX1916

Low-Dropout, Constant-Current

Triple White LED Bias Supply

________________________________________________________________ Maxim Integrated Products 1

19-2067; Rev 0; 7/01

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

General Description

The MAX1916 low-dropout bias supply for white LEDs

is a high-performance alternative to the simple ballast

resistors used in conventional white LED designs. The

MAX1916 uses a single resistor to set the bias current

for three LEDs, which are matched to 0.3%. The

MAX1916 consumes only 40µA of supply current when

enabled and 0.05µA when disabled.

The MAX1916’s advantages over ballast resistors

include significantly better LED-to-LED bias matching,

much lower bias variation with supply voltage variation,

significantly lower dropout voltage, and in some appli-

cations, significantly improved efficiency. The MAX1916

requires a 200mV dropout at a 9mA load on each out-

put to match the LED brightness.

The MAX1916 is available in a space-saving 6-pin Thin

SOT23 package.

Applications

Next-Generation Wireless Handsets

PDAs, Palmtops, and Handy Terminals

Digital Cameras, Camcorders

Battery-Powered Equipment

Features

♦ Low 200mV Dropout at 9mA

♦ Up to 60mA/LED Bias Current

♦ 0.3% LED Current Matching

♦ Simple LED Brightness Control

♦ Low 40µA Supply Current

♦ Low 0.05µA Shutdown Current

♦ 2.5V to 5.5V Supply Voltage Range

♦ Thermal Shutdown Protection

♦ Tiny 6-Pin Thin SOT23 Package (1mm High)

GND

LED3SET

16LED1

5 LED2

MAX1916

THIN SOT23-6

TOP VIEW

Pin Configuration

MAX1916

OFF

GND

SET

LED1 LED2 LED3

CTRL

V+

Typical Operating Circuit

Ordering Information

PART TEMP. RANGE

PIN-

PACKAGE

TOP

MARK

MAX1916EZT

-40°C to +85°C

6 Thin SOT23

AAAG

Summary of content (7 pages)

PAGE 1
9-2067; Rev 0; 7/01 Low-Dropout, Constant-Current Triple White LED Bias Supply The MAX1916 low-dropout bias supply for white LEDs is a high-performance alternative to the simple ballast resistors used in conventional white LED designs. The MAX1916 uses a single resistor to set the bias current for three LEDs, which are matched to 0.3%. The MAX1916 consumes only 40µA of supply current when enabled and 0.05µA when disabled.
PAGE 2
MAX1916 Low-Dropout, Constant-Current Triple White LED Bias Supply ABSOLUTE MAXIMUM RATINGS EN, SET, LED1, LED2, LED3 to GND ..................... -0.3V to +6V Continuous Power Dissipation (TA = +70°C) 6-Pin Thin SOT23 (derate 9.1mW/°C above +70°C) ... 727mW Operating Temperature Range ......................... -40°C to +85°C Storage Temperature Range ........................... -65°C to +150°C Lead Temperature (soldering, 10s)...................................
PAGE 3
Low-Dropout, Constant-Current Triple White LED Bias Supply OUTPUT CURRENT vs. VEN SUPPLY VOLTAGE LED3 LED2 10 LED1 20.0 19.9 LED CURRENT (mA) 15 OUTPUT CURRENT (mA) LED CURRENT (mA) 20 20 15 10 5 5 MAX1916 toc03 MAX1916 toc01 25 LED CURRENT vs. TEMPERATURE MAX1916 toc02 LED CURRENT vs. V+ BIAS VOLTAGE 19.8 19.7 19.6 UNMATCHED LEDS 0 0 3 4 5 19.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.
PAGE 4
Typical Operating Characteristics (continued) (VEN = 3.3V, VCTRL = 3.3V, RSET = 24.9kΩ, V+ = 5V, TA = +25°C, unless otherwise noted.) (Circuit of Figure 1) IEN SUPPLY CURRENT vs. VEN SUPPLY VOLTAGE ENABLE AND SHUTDOWN RESPONSE MAX1916 toc08 MAX1916 toc07 45 40 IEN SUPPLY CURRENT (µA) MAX1916 Low-Dropout, Constant-Current Triple White LED Bias Supply 35 VEN 2V/div 0 30 25 20 20mA 15 ILED 20mA/div 0 10 5 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.
PAGE 5
Low-Dropout, Constant-Current Triple White LED Bias Supply PIN NAME FUNCTION 1 EN 2 GND Ground 3 SET Bias Current Set Input. The current flowing into SET sets the bias current into each LED by ILED_= 230 x ISET. VSET is internally biased to 1.215V. SET is high impedance when EN is low. 4 LED3 LED 3 Cathode Connection. Current flowing into LED3 is 230 times the current flowing into SET. LED3 is high impedance when EN is low. 5 LED2 LED 2 Cathode Connection.
PAGE 6
MAX1916 Low-Dropout, Constant-Current Triple White LED Bias Supply Setting the Output Current V+ SET controls the LED bias current. Current flowing into LED1, LED2, and LED3 is 230 times greater than the current flowing into SET. Set the output current as follows: TO OTHER CIRCUITS EXISTING VCTRL LDO SET ILED _ = 230 LED1 LED2 LED3 ON EN OFF (VCTRL − VSET ) RSET where V SET = 1.215V, V CTRL is an external voltage between 1.8V and 5.
PAGE 7
Low-Dropout, Constant-Current Triple White LED Bias Supply Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.