Datasheet

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General Description

The MAX8570 family of LCD step-up converters uses

an internal n-channel switch and an internal p-channel

output isolation switch. These converters operate from

a 2.7V to 5.5V supply voltage and deliver up to 28V at

the output.

A unique control scheme provides the highest efficien-

cy over a wide range of load conditions. The internal

MOSFET switch reduces external component count and

a high switching frequency (up to 800kHz) allows for

tiny surface-mount components. Three current-limit

options are available. The MAX8570 and MAX8572 use

a 110mA current limit to reduce ripple and component

size in low-current applications. For high-power require-

ments, the MAX8574 and MAX8575 use a 500mA cur-

rent limit and supply up to 20mA at 20V. The MAX8571

and MAX8573 use a 250mA current limit for a compro-

mise between ripple and power. Built-in safety features

protect the internal switch and down-stream compo-

nents from fault conditions.

Additional features include a low quiescent current and

a True Shutdown™ mode to save power. The MAX8570/

MAX8571/MAX8574 allow the user to set the output

voltage between 3V and 28V, and the MAX8572/

MAX8573/MAX8575 have a preset 15V output. These

step-up converters are ideal for small LCD panels with

low current requirements, but can also be used in other

applications. The MAX8571 evaluation kit is available to

help reduce design time.

Applications

LCD Bias Generators

Polymer LEDs (OLED)

Cellular or Cordless Phones

Palmtop Computers

Personal Digital Assistants (PDAs)

Organizers

Handy Terminals

Features

♦ 15V or Adjustable Output Voltage Up to 28V

♦ Safety Features Protect Against Output Faults

♦ 20mA at 20V from a Single Li+ Battery

♦ True Shutdown

♦ 87% Efficiency

♦ Up to 800kHz Switching Frequency

♦ Small, 6-Pin SOT23 and µDFN (MAX8570 Only)

Packages

MAX8570–MAX8575

High-Efficiency LCD Boost

with True Shutdown

________________________________________________________________

Maxim Integrated Products

Ordering Information

19-3329; Rev 3; 3/10

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com

EVALUATION KIT

AVAILABLE

PART TEMP RANGE

PIN-

PACKAGE

TOP

MARK

MAX8570ELT+T -40°C to +85°C 6L μDFN ACW

MAX8570EUT+T -40°C to +85°C 6 SOT23 ABTJ

MAX8571EUT+T -40°C to +85°C 6 SOT23 ABTK

MAX8572EUT+T -40°C to +85°C 6 SOT23 ABTL

MAX8573EUT+T -40°C to +85°C 6 SOT23 ABTM

MAX8574EUT+T -40°C to +85°C 6 SOT23 ABTN

MAX8575EUT+T -40°C to +85°C 6 SOT23 ABTO

GND

5SW

MAX8570

MAX8571

MAX8574

SOT23

TOP VIEW

34SHDN

Pin Configurations

PART

CURRENT LIMIT

OUTPUT VOLTAGE

MAX8570 110mA Adjustable

MAX8571 250mA Adjustable

MAX8572 110mA 15V

MAX8573 250mA 15V

MAX8574 500mA Adjustable

MAX8575 500mA 15V

Selector Guide

True Shutdown is a trademark of Maxim Integrated Products, Inc.

MAX8572

MAX8573

MAX8575

OUT

GND

OFF

= 2.7V TO 5.5V

OUT

= V

TO 28V

SHDN

Typical Operating Circuit

Denotes a lead(Pb)-free RoHS-compliant package.

T = Tape and reel.

Pin Configurations continued at end of data sheet.

Summary of content (11 pages)

PAGE 1
9-3329; Rev 3; 3/10 KIT ATION EVALU E L B AVAILA High-Efficiency LCD Boost with True Shutdown Features ♦ 15V or Adjustable Output Voltage Up to 28V ♦ Safety Features Protect Against Output Faults ♦ 20mA at 20V from a Single Li+ Battery ♦ ♦ ♦ ♦ True Shutdown 87% Efficiency Up to 800kHz Switching Frequency Small, 6-Pin SOT23 and µDFN (MAX8570 Only) Packages Ordering Information PART TEMP RANGE PINPACKAGE MAX8570ELT+T -40°C to +85°C 6L μDFN MAX8570EUT+T -40°C to +85°C 6 SOT23 ABTJ MAX8571EUT+T
PAGE 2
MAX8570–MAX8575 High-Efficiency LCD Boost with True Shutdown ABSOLUTE MAXIMUM RATINGS VCC, SHDN to GND ..................................................-0.3V to +6V SW to GND .................................................-0.3V to (VCC + 0.3V) FB to GND (MAX8570/MAX8571/ MAX8574)...............................................-0.3V to (VCC + 0.3V) OUT to GND (MAX8572/MAX8573/MAX8575) .......-0.3V to +30V LX to GND ..............................................................-0.3V to +30V ILX, ICC ......
PAGE 3
High-Efficiency LCD Boost with True Shutdown (VCC = V SHDN = 3.6V, SW open, VFB = 1.3V (MAX8570/MAX8571/MAX8574) or VOUT = 16V (MAX8572/MAX8573/MAX8575), TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER CONDITIONS SW PMOS Current Limit SW PMOS On-Resistance MIN TYP MAX VCC = 3.6V, VSW = 0V, VFB = 0V, ICC (peak) 0.45 0.75 1.10 VCC = 3.6V, VSW = 0V, VFB = 0V, ICC (average) 0.15 0.30 0.60 VCC = 2.
PAGE 4
Typical Operating Characteristics (continued) (MAX8571, VCC = 3.6V, VOUT = 18V, Circuit of Figure 2, TA = +25°C, unless otherwise noted.) 1mA LOAD 70 60 50 MAX8570, MURATA LQH32CN220K23 90 80 MAX8571, MURATA LQH32CN220K23 70 MAX8574, TOKO A914BYW-220M 60 100 MAX8570, L1 = MURATA LQH32CN470K23 90 EFFICIENCY (%) 80 100 50 VCC = 3.6V 80 MAX8571, L1 = TOKO A914BYW-470M 70 60 50 L1 = MURATA LQH32CN220K23 40 0 2 4 6 8 10 12 40 0.
PAGE 5
High-Efficiency LCD Boost with True Shutdown LOAD TRANSIENT STARTUP AND SHUTDOWN WAVEFORMS MAX8570/71/73/74/75 toc15 MAX8570/71/73/74/75 toc16 5V/div VSHDN VOUT 100mV/div (AC-COUPLED) BOOST SOFT-START SW TURN-ON 10V/div VOUT 0 5mA/div IOUT 0 ILX 200mA/div 0 100µs/div 400µs/div 1.8Ω LOAD Pin Description PIN MAX8570 (µDFN) MAX8570/ MAX8572/ MAX8571/ MAX8573/ MAX8574 MAX8575 (SOT23) (SOT23) NAME FUNCTION 3 1 — FB Feedback for Setting the Output Voltage.
PAGE 6
MAX8570–MAX8575 High-Efficiency LCD Boost with True Shutdown VCC SW LX SHDN THERMAL SHUTDOWN OUT (MAX8572/MAX8573/ MAX8575 ONLY) ILIM MAX8570– MAX8575 CONTROL LOGIC FB (MAX8570/MAX8571/ MAX8574 ONLY) EA 1.226V GND Figure 1. Functional Diagram L1 22μH L1 22μH D1 C3 4.7μF VCC = 2.7V TO 5.5V C1 1μF ON VCC VOUT = VCC TO 28V LX SW MAX8570 MAX8571 MAX8574 C4 10pF R1 D1 C2 1μF C3 4.7μF VCC = 2.7V TO 5.
PAGE 7
High-Efficiency LCD Boost with True Shutdown The MAX8570 family of compact, step-up DC-DC converters operates from a 2.7V to 5.5V supply. Consuming only 25µA of supply current, these ICs include an internal MOSFET switch with a low on-resistance. A trueshutdown feature disconnects the battery from the load and reduces the supply current to 0.05µA (typ). These DC-DC converters are available with either a fixed 15V output or are adjustable up to 28V.
PAGE 8
MAX8570–MAX8575 High-Efficiency LCD Boost with True Shutdown Table 1. Protection Features RESULT WITH COMPETING STEP-UP CONVERTERS COMMON APPLICATION FAULTS RESULT WITH MAX8570 FAMILY OUT voltage rises until the output capacitor is destroyed and/or downstream components are damaged. Converter stops switching. Output cap missing and FB open. OUT voltage rises until the output capacitor is destroyed and/or downstream components are damaged.
PAGE 9
High-Efficiency LCD Boost with True Shutdown Applications Information PC Board Layout Careful printed circuit layout is important for minimizing ground bounce and noise. Keep the GND pin and ground pads for the input and output capacitors as close together as possible. Keep the connection to LX as short as possible. Locate the feedback resistors as close as possible to the FB pin and keep the feedback traces routed away from noisy areas such as LX. Refer to the MAX8571EVKIT for a layout example.
PAGE 10
High-Efficiency LCD Boost with True Shutdown MAX8570–MAX8575 Pin Configurations (continued) TOP VIEW + + SHDN 1 GND 2 MAX8570 FB 3 6 LX OUT 1 5 SW GND 2 4 VCC SHDN 3 μDFN 5 SW 4 LX Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 10 VCC SOT23 Chip Information PROCESS: BiCMOS MAX8572 MAX8573 MAX8575 6 PACKAGE CODE DOCUMENT NO.
PAGE 11
High-Efficiency LCD Boost with True Shutdown REVISION NUMBER REVISION DATE 2 8/09 Added μDFN package 3/10 Added soldering temperature, corrected unit of measurement error, and updated figure reference 3 DESCRIPTION PAGES CHANGED 1, 2, 5, 9, 10 2, 5, 9 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.