Maxim MAX1698EUB Datasheet

General Description

The MAX1698 is the most efficient driver for white or
color LEDs. The device is ideal for LED backlit displays
in PDAs and digital cameras, and can also be used for
larger displays like those in laptop computers. Its
numerous benefits include greater simplicity, lower
cost, higher efficiency, longer bulb life, and greater reli­ability when compared to fluorescent (CCFL) and elec­troluminescent (EL) lamps.

The MAX1698 is a switch-mode boost controller in
which LED current, rather than output voltage, provides
the feedback signal. It can operate with battery inputs
as low as 0.8V. The device drives series-connected
LEDs with a controlled current that is measured at a
sense resistor connected at the feedback pin. The
required sense resistor is typically 15Ω, not an expen­sive fractional-ohm value. LED current control and dim­ming are accomplished with an adjust input (ADJ), not
with lossy current-limiting resistors. For larger light out­put, multiple LED banks can be connected in parallel
with up to 5W total output power.

The MAX1698 is supplied in a space-saving 10-pin
µMAX package that occupies half the space of an 8-pin
SO. An evaluation kit (MAX1698EVKIT) is available to
speed designs.

Applications

Battery-Powered Backlight Applications

Backlight for LCD Panels

Cell Phones

Handy Terminals

PDAs

Features

♦ Over 90% Efficiency

♦ Lossless, Adjustable LED Brightness

♦ Space-Saving 10-Pin µMAX Package

♦ Simpler, Lower Cost, More Reliable Compared

to CCFL or EL Backlights

♦ Up to 5W Output Power

MAX1698

High-Efficiency Step-Up

Current Regulator for LEDs

________________________________________________________________ Maxim Integrated Products 1

Typical Operating Circuit

19-1621; Rev 0; 1/00

PART

MAX1698EUB

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

10 µMAX

EVALUATION KIT

AVAILABLE

Pin Configuration

Ordering Information

For free samples and the latest literature, visit www.maxim-ic.com or phone [phone].
For small orders, phone [phone].

TOP VIEW

V

SHDN

REF

1

CC

2

MAX1698

3

4

5

10

9

8

7

6

EXT

CS

PGND

GNDADJ

FBGND

V

CC

SHDN

REF

ADJ

GND

L

EXT

MAX1698

CS

PGND

FB

V

BATT

V

CC

OFF

ON

µMAX

D1

I

LED

R

FB

R

N

V

OUT

C

OUT

MAX1698

High-Efficiency Step-Up
Current Regulator for LEDs

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

VCC, SHDN to GND..................................................-0.3V to +6V

EXT, FB, CS, ADJ, REF to GND..................-0.3V to (V

CC

+ 0.3V)

GND to PGND.....................................................................±0.3V

Continuous Power Dissipation (T

A

= +70°C)

10-Pin µMAX (derate 5.6mW/°C above +70°C) ............444mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature Range (soldering, 10s)......................+300°C

FB = GND, ADJ = REF, CS = GND

FB = GND, ADJ = REF

Rising edge

FB = GND

VFB= 0.3V

ADJ = REF

V

ADJ

= 100mV

CONDITIONS

mV30 50 70ADJ Start Threshold

µs10 15 20t

ON(MAX)

Maximum On Time

µs0.8 1.0 1.2t

OFF(MIN)

Minimum Off Time

A

RMS

0.8I

CS

CS Input Current

A0.8 1.5 2.5CS Trip Current

V2.25 2.4 2.55Undervoltage Lockout

µA260 500I

CC

V2.7 5.5V

CC

Supply Voltage

Quiescent Supply Current

mV80Undervoltage Hysteresis

285 300 315

mV

18 24 30

V

FB

FB Regulation Voltage

UNITSMIN TYP MAXSYMBOLPARAMETER

VFB= 300mV nA-15 15I

FB

FB Input Bias Current

V0.03 REFV

ADJ

ADJ Input Range

ADJ Input Bias Current I

ADJ

ADJ = REF -50 50 nA

Shutdown Supply Current

SHDN = GND

0.01 1 µA

REF Output Voltage V

REFIREF

= 0 1.20 1.25 1.30 V

REF Load Regulation ∆V

REFIREF

= 0 to 150µA -2 -25 mV

REF Short-Circuit Current REF = GND 0.45 1 mA

REF Power-Supply Rejection
Ratio

PSRR VCC= 2.7V to 5.5V +0.3 +2 mV/V

EXT Driver Sink/Source Current VCC= 5V, EXT = 2V 0.2 A

EXT Driver On-Resistance VCC= 5V 8 Ω
SHDN Input High Voltage

V

IH

VCC= 2.7V to 5.5V 2 V

SHDN Input Low Voltage

V

IL

VCC= 2.7V to 5.5V 0.8 V

SHDN Input Bias Current

I

SHDN

VCC= 2.7V to 5.5V -1 1 µA

MAX1698

High-Efficiency Step-Up

Current Regulator for LEDs

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS

(VCC= +3.3V, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

CONDITIONS

VV

CC

Supply Voltage 2.7 5.5

UNITSMIN MAXSYMBOLPARAMETER

CS Trip Current FB = GND 0.8 3.0 A

Minimum Off Time t

OFF(MIN)

FB = GND, ADJ = REF 0.6 1.4 µs

Maximum On Time t

ON(MAX)

FB = GND, ADJ = REF, CS = GND 921µs

ADJ Start Threshold 25 75 mV

FB Input Bias Current I

FB

VFB= 300mV -20 20 nA

ADJ Input Bias Current I

ADJ

ADJ = REF -50 50 nA

Shutdown Supply Current

SHDN = GND

1 µA

REF Output Voltage V

REFIREF

= 0 1.17 1.33 V

REF Load Regulation ∆V

REFIREF

= 0 to 150µA -30 mV

REF Short-Circuit Current REF = GND 1 mA

REF Power-Supply Rejection
Ratio

PSRR VCC= 2.7V to 5.5V +2 mV/V

EXT On-Resistance VCC= 5V 8 Ω
SHDN Input High Voltage

V

IH

VCC= 2.7V to 5.5V 2 V

SHDN Input Low Voltage

V

IL

VCC= 2.7V to 5.5V 0.8 V

SHDN Input Bias Current

I

SHDN

VCC= 2.7V to 5.5V -1 1 µA

Note 1: Specifications to -40°C are guaranteed by design, not production tested.

Rising edge VUndervoltage Lockout 2.20 2.65

V

ADJ

= 100mV

ADJ = REF

mV

13 35

V

FB

FB Regulation Voltage

280 320

VFB= 0.3V µAI

CC

Quiescent Supply Current 500