19-2011; Rev 3; 4/05
WCDMA Cellular Phone 600mA
Buck Regulators
General Description
Features
The MAX1820/MAX1821 low-dropout, pulse-width-mod-
ulated (PWM) DC-DC buck regulators are optimized to
provide power to the power amplifier (PA) in WCDMA
cell phones; however, they may be applied in many
other applications where high efficiency is a priority. The
supply voltage range is from 2.6V to 5.5V, and the guar-
anteed output current is 600mA; 1MHz PWM switching
allows for small external components, while skip mode
reduces quiescent current to 180µA with light loads.
♦ Dynamically Adjustable Output from 0.4V to 3.4V
(MAX1820)
♦ Programmable Output from 1.25V to 5.5V
(MAX1821)
♦ SYNC to 13MHz External Clock (MAX1820X)
♦ SYNC to 19.8MHz External Clock (MAX1820Y)
♦ NO SYNC, Internal 1MHz Oscillator (MAX1820Z)
The MAX1820 is dynamically controlled to provide vary-
ing output voltages from 0.4V to 3.4V. The circuit is
designed such that the output voltage settles in <30µs
for a full-scale change in voltage and current. The
MAX1821 is set with external resistors to provide any
fixed output voltage in the 1.25V to 5.5V range.
♦ Low Quiescent Current
180µA (typ) in Skip Mode
0.1µA (typ) in Shutdown Mode
♦ No External Schottky Diode Required
♦ 600mA Guaranteed Output Current
♦ 0% to 100% Duty-Cycle Operation
The MAX1820/MAX1821 include a low on-resistance
internal MOSFET switch and synchronous rectifier to
maximize efficiency and minimize external component
count; 100% duty-cycle operation allows for low dropout
of only 150mV at 600mA load, including the external
inductor resistance. The devices are offered in 10-pin
♦ 150mV Dropout at 600mA Load (Including R
of External Inductor)
DC
♦ µMAX or UCSP Packaging
®
✕
µMAX and tiny 3 4 chip-scale (UCSP™) packages.
Typical Operating Circuits
________________________Applications
4.7µH
INPUT
2.6V TO
5.5V
DYNAMIC
OUTPUT
WCDMA Cell Phone Power Amplifiers
PDA, Palmtop, and Notebook Computers
Microprocessor Core Supplies
Digital Cameras
BATT
LX
0.4V TO 3.4V
OUT
SHDN
4.7µF
PGND
MAX1820
13MHz
OR
19.8MHz
PCMCIA and Network Cards
Hand-Held Instruments
COMP
GND
SYNC
V
OUT
CONTROL
DAC
REF
Typical Operating Circuits continued at end of data sheet.
Ordering Information continued at end of data sheet.
Pin Configurations appear at end of data sheet.
SKIP
UCSP is a trademark of Maxim Integrated Products, Inc.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Ordering Information
SYNC
PART
OUTPUT VOLTAGE
TEMP RANGE
PIN-PACKAGE
UCSP MARK
FREQ (MHz)
No Sync
19.8
✕
✕
✕
MAX1820ZEBC*
MAX1820YEBC*
MAX1820XEBC*
MAX1820ZEUB
MAX1820YEUB
MAX1820XEUB
Dynamic
Dynamic
Dynamic
Dynamic
Dynamic
Dynamic
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
3
3
3
4 UCSP
4 UCSP
4 UCSP
AAB
AAL
AAM
—
13
No Sync
19.8
10 µMAX
10 µMAX
10 µMAX
—
13
—
*UCSP reliability is integrally linked to the user’s assembly methods, circuit board material, and environment. See the UCSP Reliability
Notice in the UCSP Reliability section of this data sheet for more information.
________________________________________________________________ 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.