MAX1927 Datasheet, PDF (1/12 Pages) Maxim Integrated Products – Low-Output-Voltage, 800mA, PWM Step-Down DC-DC Converters

19-2527; Rev 0; 7/02
Low-Output-Voltage, 800mA, PWM Step-Down
DC-DC Converters
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
o 800mA Output Current
o Output Voltages from 0.75V to 5V
o 2.6V to 5.5V Input Voltage Range
o Power-OK Output
o No Schottky Diode Required
o Selectable Forced PWM Operation
o 1MHz Fixed-Frequency PWM Operation
o 140µA Quiescent Current
o Soft-Start
o 10-Pin µMAX Package
Ordering Information
PART
MAX1927REUB
MAX1928EUB15
MAX1928EUB18
MAX1928EUB25
PRESET
OUTPUT
VOLTAGE
TEMP
RANGE
PIN-
PACKAGE
Adj. to 0.75V -40°C to +85°C 10 µMAX
1.5V
-40°C to +85°C 10 µMAX
1.8V
-40°C to +85°C 10 µMAX
2.5V
-40°C to +85°C 10 µMAX
Pin Configuration
TOP VIEW
PWM 1
GND 2
REF 3
FB 4
COMP 5
MAX1927R
MAX1928
10 POK
9 BATT
8 LX
7 PGND
6 SHDN
µMAX
Typical Operating Circuit
V_IN
2.6V TO 5.5V
BATT
C1
PWM
LX
SHDN
FB
R_C
MAX1927R
COMP
POK
C_C
C_f
L1
V_OUT
0.75V AT 800mA
C2
REF
PGND
GND
________________________________________________________________ Maxim Integrated Products 1
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.