Rainbow Electronics MAX1734 User Manual

General Description

The MAX1733/MAX1734 step-down DC-DC converters
deliver over 250mA to outputs as low as 1.25V. These
converters use a unique proprietary current-limited con­trol scheme that achieves over 90% efficiency. These
devices maintain extremely low quiescent supply cur­rent (40µA), and their high 1.2MHz (max) operating fre­quency permits small, low-cost external components.
This combination of features makes the MAX1733/
MAX1734 excellent high-efficiency alternatives to linear
regulators in space-constrained applications.

Internal synchronous rectification greatly improves effi­ciency and eliminates the external Schottky diode
required in conventional step-down converters. Both
devices also include internal digital soft-start to limit
input current upon startup and reduce input capacitor
requirements.

The MAX1733 provides an adjustable output voltage
(1.25V to 2.0V). The MAX1734 provides factory-preset
output voltages (see Selector Guide). Both are avail­able in space-saving 5-pin SOT23 packages.

Applications

Cellular, PCS, and Cordless Telephones

PDAs, Palmtops, and Handy-Terminals

Battery-Powered Equipment

Features

♦ 250mA Guaranteed Output Current

♦ Synchronous Rectifier for Over 90% Efficiency

♦ Tiny 5-Pin SOT23 Package

♦ 40µA Quiescent Supply Current

♦ 0.01µA Logic-Controlled Shutdown

♦ Up to 1.2MHz Switching Frequency

♦ Fixed 1.8V or 1.5V Outputs (MAX1734)

♦ Adjustable Output Voltage (MAX1733)

♦ ±1.5% Initial Accuracy

♦ 2.7V to 5.5V Input Range

♦ Soft-Start Limits Startup Current

MAX1733/MAX1734

Low-Voltage, Step-Down DC-DC Converters

in SOT23

________________________________________________________________ Maxim Integrated Products 1

GND

OUT (FB)

( ) ARE FOR MAX1733 ONLY.

SHDN

15LXIN

MAX1733
MAX1734

SOT23-5

TOP VIEW

2

34

Pin Configuration

OUT

V

OUT

AT

250mA

INPUT

+2.7V TO +5.5V

LX

IN

MAX1734

SHDN

GND

10µH

22µF

2.2µF

Typical Operating Circuit

19-1586; Rev 0; 7/00

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

Note: The MAX1734 offers two output voltages. See the Selector

Guide, then insert the proper designator into the blanks above to
complete the part number.

Ordering Information

Selector Guide

PART TEMP. RANGE PIN-PACKAGE

MAX1733EUK-T -40°C to +85°C 5 SOT23-5
M A X1 7 3 4 E U K_ _- T -40°C to +85°C 5 SOT23-5

PART V

MAX1733EUK Adjustable ADKY

MAX1734EUK18 1.8 ADKW

MAX1734EUK15 1.5 ADKX

(V) TOP MARK

OUT

MAX1733/MAX1734

Low-Voltage, Step-Down DC-DC Converters
in SOT23

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= +2.7V to +5.5V, SHDN = IN, TA= 0°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.)

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.

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

OUT, FB, LX to GND....................................-0.3V to (V

IN

+ 0.3V)

OUT Short Circuit to GND ..........................................Continuous

Continuous Power Dissipation (T

A

= +70°C)

5-Pin SOT23 (derate 7.1mW/°C above +70°C)............571mW

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

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

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

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

)

Input Voltage Range V

Startup Voltage V

UVLO Threshold V

UVLO Hysteresis 200 mV

Quiescent Supply Current I

Shutdown Supply Current I

Outp ut V ol tag e Range ( MAX 1733) V

Output Voltage Accuracy
(MAX1734)

Load Regulation I

Line Regulation VIN = 2.7V to 5.5V 0 %/V

OUT Sense Current (MAX1734) V

FB Feedback Threshold
(MAX1733)

FB Leakage Current (MAX1733) I

SHDN Input High Voltage V
SHDN Input Low Voltage V
SHDN Leakage Current I

High-Side Current Limit I

Low-Side Current Limit I

High-Side On-Resistance R

Rectifier On-Resistance R

Rectifier Off-Current Threshold I

LX Leakage Current I

LX Reverse Leakage Current I

Minimum On-Time t

Minimum Off-Time

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

START

UVLO

IN

SHDN

OUT

V

FB

FB

SHDN

LIMP

LIMN

ONP

ONN

LXOFF

LXLEAKVIN

LXLK,R

ON(MIN

t

OFF( M IN)

VIN rising 1.85 1.95

VIN falling 1.55 1.65

No switching, no load (FB/OUT above trip
point)

SHDN = GND 0.01 4 µA

I

= 0, TA = +25°C -1.5 +1.5

OUT

I

= 0 to 250mA -3 +3

OUT

= 0 to 250mA 0 %/mA

OUT

= V

OUT

REG

TA = +25°C, VIN = 3.6V 1.231 1.250 1.269

VIN = 3.6V 1.220 1.280

V

= 1.5V 0.001 0.2 µA

FB

2.7V < VIN < 5.5V 1.6 V

IH

2.7V < VIN < 5.5V 0.4 V

IL

SHDN = GND or IN 0.001 1 µA

I

= -50mA, VIN = 3.0V 0.7 1.4

LX

I

= -50mA, VIN = 5.5V 0.5 1.1

LX

I

= -50mA, VIN = 3.0V 1.0 2

LX

I

= -50mA, VIN = 5.5V 0.8 1.6

LX

= 5.5V, VLX = 0 to V

IN unconnected, VLX = 5.5V, SHDN = GND 0.1 5 µA

VIN = 3.6V 0.28 0.4 0.5 µs

VIN = 3.6V 0.28 0.4 0.5 µs

2.7 5.5 V

40 70 µA

1.25 2.0 V

, VIN = V

= 5V 4 8 µA

SHDN

300 425 535 mA

200 325 430 mA

40 mA

IN

0.1 5 µA

2.0 V

V

%

V

Ω

Ω

MAX1733/MAX1734

Low-Voltage, Step-Down DC-DC Converters

in SOT23

_______________________________________________________________________________________ 3

Note 1: All devices are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by design.

ELECTRICAL CHARACTERISTICS

(VIN= +2.7V to +5.5V, SHDN = IN, TA= -40°C to +85°C, unless otherwise noted.) (Note 1)

)

Input Voltage Range V

Startup Voltage V

UVLO Threshold V

Quiescent Supply Current I

Shutdown Supply Current I

Outp ut V ol tag e Range ( MAX 1733) V

Output Voltage Accuracy
(MAX1734)

OUT Sense Current (MAX1734) I

FB Feedback Threshold
(MAX1733)

FB Leakage Current (MAX1733) I

SHDN Input High Voltage V
SHDN Input Low Voltage V
SHDN Leakage Current I

High-Side Current Limit I

Low-Side Current Limit I

High-Side On-Resistance R

Rectifier On-Resistance R

LX Leakage Current I

LX Reverse Leakage Current I

Minimum On-Time t

Minimum Off-Time

PARAMETER SYMBOL CONDITIONS MIN MAX UNITS

IN

START

UVLO

IN

SHDN

OUT

OUT

V

FB

FB

SHDN

LIMP

LIMN

ONP

ONN

LXLEAKVIN

LXLK,R

ON(MIN

t

OFF( M IN)

VIN rising, 200mV typical hysteresis 1.95

VIN falling 1.55
No switching (FB/OUT above trip point) 70 µA
SHDN = GND 4 µA

= 0 to 250mA -3 +3 %

I

OUT

V

= V

REG

, VIN = V

OUT

VIN = 3.6V 1.210 1.280 V

V

= 1.5V 0.2 µA

FB

2.7V < VIN < 5.5V 1.6 V

IH

2.7V < VIN < 5.5V 0.4 V

IL

SHDN = GND or IN 1 µA

ILX = -50mA, VIN = 3.0V 1.4

ILX = -50mA, VIN = 5.5V 1.1

ILX = -50mA, VIN = 3.0V 2

ILX = -50mA, VIN = 5.5V 1.6

= 5.5V, VLX = 0 to V

IN unconnected, VLX = 5.5V, SHDN = GND 5 µA

= 5V 8 µA

SHDN

IN

2.7 5.5 V

2.0 V

V

1.25 2.0 V

300 565 mA

200 430 mA

Ω

Ω

5 µA

0.25 0.55 µs

0.25 0.55 µs