MAX1928EUB15+ Datasheet MAX1928EUB15+, MAX1927REUB+, MAX1928EUB15+T | P1-P3

General Description

The MAX1927/MAX1928 800mA step-down converters

power low-voltage microprocessors in compact equip-

ment requiring the highest possible efficiency. The

MAX1927/MAX1928 are optimized for generating low

output voltages (down to 750mV) at high efficiency

using small external components. The supply voltage

range is from 2.6V to 5.5V and the guaranteed minimum

output current is 800mA. 1MHz pulse-width modulation

(PWM) switching allows for small external components.

A unique control scheme minimizes ripple at light loads,

while maintaining a low 140µA quiescent current.

The MAX1927/MAX1928 include a low on-resistance

internal MOSFET switch and synchronous rectifier to

maximize efficiency and minimize external component

count. No external diode is needed. 100% duty-cycle

operation allows for a dropout voltage of only 340mV at

800mA. Other features include internal soft-start,

power-OK (POK) output, and selectable forced PWM

operation for lower noise at all load currents.

The MAX1928 is available with several preset output

voltages: 1.5V (MAX1928-15), 1.8V (MAX1928-18), and

2.5V (MAX1928-25). The MAX1927R has adjustable

output range down to 0.75V. The MAX1927/MAX1928

are available in a tiny 10-pin µMAX package.

Applications

WCDMA Handsets

PDAs and Palmtops

DSP Core Power

Battery-Powered Equipment

Features

♦ 800mA Output Current

♦ Output Voltages from 0.75V to 5V

♦ 2.6V to 5.5V Input Voltage Range

♦ Power-OK Output

♦ No Schottky Diode Required

♦ Selectable Forced PWM Operation

♦ 1MHz Fixed-Frequency PWM Operation

♦ 140µA Quiescent Current

♦ Soft-Start

♦ 10-Pin µMAX Package

MAX1927/MAX1928

Low-Output-Voltage, 800mA, PWM Step-Down

DC-DC Converters

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

BATT

COMP

GND

REF

PGND

POK

2.6V TO 5.5V

OUT

0.75V AT 800mA

SHDN

PWM

MAX1927R

Typical Operating Circuit

19-2527; Rev 0; 7/02

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.

PART

PRESET

OUTPUT

VOLTAGE

TEMP

RANGE

PIN-

PACKAGE

MAX1927REUB

Adj. to 0.75V -40°C to +85°C

10 µMAX

MAX1928EUB15

1.5V

-40°C to +85°C

10 µMAX

MAX1928EUB18

1.8V

-40°C to +85°C

10 µMAX

MAX1928EUB25

2.5V

-40°C to +85°C

10 µMAX

POK

BATT

PGNDFB

REF

GND

PWM

MAX1927R

MAX1928

µMAX

TOP VIEW

COMP SHDN

Pin Configuration

MAX1927/MAX1928

Low-Output-Voltage, 800mA, PWM Step-Down

DC-DC Converters

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

BATT

= 3.6V, SHDN = BATT, C

REF

= 0.1µF, T

= 0°C to +85°C, unless otherwise noted. Typical values are at T

= +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.

BATT, PWM, POK, COMP, SHDN to GND ...............-0.3V to +6V

PGND to GND .......................................................-0.3V to +0.3V

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

BATT

+ 0.3V)

Continuous Power Dissipation (T

= +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 (soldering, 10s) .................................+300°C

PARAMETER CONDITIONS

MIN

TYP

MAX

UNITS

BATT Input Voltage 2.6 5.5 V

Undervoltage Lockout Threshold V

BATT

rising or falling (35mV hysteresis)

2.15 2.35

2.55

No load, pulse skipping, PWM = GND

140

240 µA

Quiescent Current

1MHz switching 2 mA

Quiescent Current in Dropout

190

340 µA

Shutdown Supply Current SHDN = GND 0.1 10 µA

REFERENCE AND ERROR AMP

MAX1927R

0.738 0.75 0.762

MAX1928-15

1.477

1.5

1.523

MAX1928-18

1.773

1.8

1.827

FB Voltage Accuracy

MAX1928-25

2.462

2.5

2.538

MAX1928 5 10 15 µA

FB Input Current

MAX1927R 10 150 nA

MAX1927R

250

MAX1928-15

210

MAX1928-18

175

Transconductance (g

)

MAX1928-25

125

µS

Reference Voltage Accuracy

1.231 1.25 1.269

Reference Supply Rejection 2.6V < V

BATT

< 5.5V 0.5 2 mV

PWM CONTROLLER

BATT

= 3.6V

0.25

0.4

P-Channel On-Resistance

BATT

= 2.6V 0.3 0.5

Ω

BATT

= 3.6V

0.17

0.3

N-Channel On-Resistance

BATT

= 2.6V 0.2

0.35

Ω

Current-Sense Transresistance (R

)

0.48

V/A

P-Channel Current-Limit Threshold 1.1 1.3 1.6 A

P-Channel Pulse-Skipping Current Threshold

0.11 0.13 0.15

N-Channel Negative Current-Limit Threshold

-0.55

MAX1927/MAX1928

Low-Output-Voltage, 800mA, PWM Step-Down

DC-DC Converters

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

BATT

= 3.6V, SHDN = BATT, C

REF

= 0.1µF, T

= 0°C to +85°C, unless otherwise noted. Typical values are at T

= +25°C.)

PARAMETER CONDITIONS

MIN TYP MAX

UNITS

N-Channel Synchronous Rectifier Turn-Off

Threshold

20 mA

LX Leakage Current V

BATT

= 5.5V, LX = GND or BATT -20 0.1

+20

µA

Maximum Duty Cycle

100

PWM = GND 0

Minimum Duty Cycle

PWM = BATT 15

Internal Oscillator Frequency

0.85

1.15

MHz

Thermal Shutdown Threshold 15°C hysteresis

160

D eg r ees

POK COMPARATOR

BATT Operating Voltage Range I

POK

= 0.1 mA 1 5.5 V

Output Low Voltage V

= 0.5V, I

POK

= 1mA

0.01

0.1 V

Output High Leakage Current V

POK

= 5.5V 1 µA

MAX1927R

0.650 0.675 0.700

MAX1928-15

1.305 1.350 1.395

MAX1928-18

1.566 1.620 1.674

POK Threshold

MAX1928-25

2.175 2.250 2.325

Output Valid to POK Release Delay

POK transitions to high impedance 20ms

after V

> V

POK

15 20 25 ms

LOGIC INPUTS (SHDN, PWM)

Logic Input High 2.6V < V

BATT

< 5.5 V 1.6 V

Logic Input Low 2.6V < V

BATT

< 5.5 V 0.6 V

Logic Input Current V

BATT

= 5.5V 0.1 1 µA

ELECTRICAL CHARACTERISTICS

BATT

= 3.6V, SHDN = BATT, C

REF

= 0.1µF, T

= -40°C to +85°C, unless otherwise noted.)

PARAMETER CONDITIONS

MIN MAX

UNITS

BATT Input Voltage 2.6 5.5 V

Undervoltage Lockout Threshold V

BATT

rising or falling (35mV hysteresis)

2.15

2.55

Quiescent Current No load, pulse skipping, PWM = GND 240 µA

Quiescent Current in Dropout 340 µA

Shutdown Supply Current SHDN = GND 10 µA

REFERENCE AND ERROR AMP

MAX1927R

0.732 0.768

MAX1928-15

1.47 1.53

MAX1928-18

1.764 1.836

FB Voltage Accuracy

MAX1928-25

2.45 2.55

FB Input Current MAX1928 5 15 µA

P1-P3 P4-P6 P7-P9 P10-P12

MAX1928EUB15+

Mfr. #:

Buy MAX1928EUB15+

Manufacturer:

Maxim Integrated

Description:

Switching Voltage Regulators 800mA PWM Step-Down DC/DC Converter

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New from this manufacturer.

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MAX1928EUB15+

MAX1928EUB15+

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