19-2011; Rev 3; 4/05
KIT
ATION
EVALU
BLE
AVAILA
WCDMA Cellular Phone 600mA
Buck Regulators
Features
♦
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)
♦
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
♦
150mV Dropout at 600mA Load (Including R
DC
of External Inductor)
♦
µMAX or UCSP Packaging
General Description
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.
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.
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
µMAX
®
and tiny 3
✕
4 chip-scale (UCSP™) packages.
MAX1820/MAX1821
________________________Applications
WCDMA Cell Phone Power Amplifiers
PDA, Palmtop, and Notebook Computers
Microprocessor Core Supplies
Digital Cameras
PCMCIA and Network Cards
Hand-Held Instruments
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.
UCSP is a trademark of Maxim Integrated Products, Inc.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
INPUT
2.6V TO
5.5V
Typical Operating Circuits
4.7µH
BATT
SHDN
LX
OUT
PGND
13MHz
OR
19.8MHz
V
OUT
CONTROL
DAC
MAX1820
COMP
SYNC
DYNAMIC
OUTPUT
0.4V TO 3.4V
4.7µF
REF
SKIP
GND
Ordering Information
TEMP RANGE
-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
PIN-PACKAGE
3
✕
4 UCSP
3
✕
4 UCSP
3
✕
4 UCSP
10 µMAX
10 µMAX
10 µMAX
UCSP MARK
AAB
AAL
AAM
—
—
—
PART
MAX1820ZEBC*
MAX1820YEBC*
MAX1820XEBC*
MAX1820ZEUB
MAX1820YEUB
MAX1820XEUB
SYNC
FREQ (MHz)
No Sync
19.8
13
No Sync
19.8
13
OUTPUT VOLTAGE
Dynamic
Dynamic
Dynamic
Dynamic
Dynamic
Dynamic
*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.
WCDMA Cellular Phone 600mA
Buck Regulators
MAX1820/MAX1821
ABSOLUTE MAXIMUM RATINGS
BATT, OUT (FB),
SHDN,
SYNC,
SKIP,
REF to GND .......................................................-0.3V to +6.0V
PGND to GND .......................................................-0.3V to +0.3V
LX, COMP to GND...................................-0.3V to (V
BATT
+ 0.3V)
Output Short-Circuit Duration ............................................Infinite
Continuous Power Dissipation (T
A
= +70°C)
3
✕
4 UCSP (derate 10.4mW/°C above +70°C)............832mW
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 Ranges
3
✕
4 UCSP ....................................................-40°C to +150°C
10-Pin µMAX ..................................................-65°C to +150°C
Solder Profile (UCSP) ......................................................(Note 1)
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
For UCSP solder profile information, visit www.maxim-ic.com/1st_pages/UCSP.htm.
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.
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V,
SHDN
= BATT,
SKIP
= SYNC = GND, V
REF
= 1.25V (MAX1820 only),
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Input BATT Voltage
Undervoltage Lockout
Threshold
SYMBOL
V
IN
V
UVLO
V
BATT
rising, 1% hysteresis
SKIP
= GND (MAX1820Z/MAX1821)
SKIP
= BATT, no switching
Quiescent Current
I
Q
SKIP
= GND (MAX1820Y, MAX1820X, and
MAX1821X)
SKIP
= BATT, 1MHz switching
Quiescent Current in Dropout
Shutdown Supply Current
ERROR AMPLIFIER
OUT Voltage Accuracy
(MAX1820)
V
REF
= 1.932
±0.005V,
load = 0 to 600mA,
SKIP
= BATT or GND
V
OUT
V
REF
= 0.227
±0.005V,
load = 0 to 30mA,
SKIP
= BATT, V
BATT
≤
4.2V
3.33
0.35
250
3.4
0.40
400
0.1
FB = COMP
V
FB
= 1.4V
30
0.2
2.04
1.225
1.25
0.01
50
0.45
2.15
1
1.275
50
85
1.0
2.28
3.47
V
0.45
kΩ
µA
V
nA
µS
V
V
I
SHDN
SKIP
= GND
SKIP
= BATT, no switching
SHDN
= GND
CONDITIONS
MIN
2.6
2.20
2.35
180
450
240
3300
530
550
0.1
1000
1000
6
µA
µA
TYP
MAX
5.5
2.55
300
2000
360
µA
UNITS
V
V
OUT Input Resistance
(MAX1820)
REF Input Current (MAX1820)
FB Voltage Accuracy
(MAX1821)
FB Input Current (MAX1821)
Transconductance
COMP Clamp Low Voltage
COMP Clamp High Voltage
R
OUT
I
REF
V
FB
I
FB
g
m
2
_______________________________________________________________________________________
WCDMA Cellular Phone 600mA
Buck Regulators
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V,
SHDN
= BATT,
SKIP
= SYNC = GND, V
REF
= 1.25V (MAX1820 only),
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
CONTROLLER
P-Channel On-Resistance
N-Channel On-Resistance
Current-Sense Transresistance
P-Channel Current-Limit
Threshold
P-Channel Pulse-Skipping
Current Threshold
N-Channel Current-Limit
Threshold
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
SYNC AND OSCILLATOR
SYNC Divide Ratio
(MAX1820X)
SYNC Capture Range
(MAX1820X)
SYNC Leakage Current
Frequency
SYNC Divide Ratio
(MAX1820Y)
SYNC Capture Range
(MAX1820Y)
Internal Oscillator Frequency
(MAX1820Z, MAX1821)
LOGIC INPUTS (SKIP,
SHDN)
Logic Input High
Logic Input Low
Logic Input Current
V
IH
V
IL
-1
0.1
1.6
0.4
1
V
V
µA
f
OSC
I
SYNC
SYNC = sine wave, SYNC input = 200mV
P-P
SYNC = sine wave, SYNC input = 800mV
P-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mV
P-P
V
SYNC
= 1V (MAX1820Z, MAX1821)
V
SYNC
= 1V (MAX1820X, MAX1820Y, and
MAX1821X)
SYNC = sine wave, SYNC input = 200mV
P-P
SYNC = sine wave, SYNC input = 800mV
P-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mV
P-P
SYNC = GND
13
13
10
-1
-5
18
18
15
0.8
19.8
1
13
13
13
16
+1
+5
18
18
21
1.2
µA
Hz/Hz
MHz
I
LX
duty
MAX
duty
MIN
SKIP
= GND
SKIP
= BATT, V
BATT
= 4.2V
P-P
P
RDS
N
RDS
R
CS
Duty factor = 100%
SKIP
= GND
SKIP
= BATT
SKIP
= GND
V
BATT
= 5.5V, LX = GND or BATT
I
LX
= 180mA, V
BATT
= 3.6V
I
LX
= 180mA, V
BATT
= 2.6V
I
LX
= 180mA, V
BATT
= 3.6V
I
LX
= 180mA, V
BATT
= 2.6V
0.25
0.75
0.04
-1.6
0.02
-1
100
0
10
0.15
0.2
0.2
0.3
0.50
1.2
0.13
-0.85
0.08
0.1
0.75
1.55
0.24
-0.45
0.14
1
0.35
0.3
Ω
Ω
V/A
A
A
A
µA
%
%
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1820/MAX1821
Hz/Hz
MHz
MHz
_______________________________________________________________________________________
3
WCDMA Cellular Phone 600mA
Buck Regulators
MAX1820/MAX1821
ELECTRICAL CHARACTERISTICS
(V
BATT
= 3.6V,
SHDN
= BATT,
SKIP
= SYNC = GND, V
REF
= 1.25V (MAX1820 only),
T
A
= -40°C to +85°C,
unless otherwise noted.)
(Notes 2, 3)
PARAMETER
Input BATT Voltage
Undervoltage Lockout
Threshold
SYMBOL
V
IN
V
UVLO
V
BATT
rising, 1% hysteresis
SKIP
= GND (MAX1820Z, MAX1821)
Quiescent Current
I
Q
SKIP
= GND (MAX1820X, MAX1820Y, and
MAX1821X)
SKIP
= BATT, no switching
Quiescent Current in Dropout
Shutdown Supply Current
ERROR AMPLIFIER
OUT Voltage Accuracy
(MAX1820)
V
REF
= 1.932 ±0.005V, load = 0 to 600mA,
SKIP
= BATT or GND
V
OUT
V
REF
= 0.227 ±0.005V, load = 0 to 30mA,
SKIP
= BATT, V
BATT
≤
4.2V
3.33
0.35
250
1
FB = COMP
V
FB
= 1.4V
30
0.2
2.04
P
RDS
N
RDS
R
CS
Duty factor = 100%
SKIP
= GND
SKIP
= BATT
SKIP
= GND
I
LX
= 180mA, V
BATT
= 3.6V
I
LX
= 180mA, V
BATT
= 3.6V
0.25
0.75
0.04
-1.6
0.01
1.225
1.275
50
85
1.0
2.28
0.3
0.35
0.75
1.55
0.24
-0.45
0.14
3.47
V
0.45
kΩ
µA
V
nA
µS
V
V
Ω
Ω
V/A
A
A
A
I
SHDN
SKIP
= GND
SKIP
= BATT, no switching
SHDN
= GND
CONDITIONS
MIN
2.6
2.15
MAX
5.5
2.55
300
360
2000
1000
1000
6
µA
µA
µA
UNITS
V
V
OUT Input Resistance
(MAX1820)
REF Input Current (MAX1820)
FB Voltage Accuracy
(MAX1821)
FB Input Current (MAX1821)
Transconductance
COMP Clamp Low Voltage
COMP Clamp High Voltage
CONTROLLER
P-Channel On-Resistance
N-Channel On-Resistance
Current-Sense Transresistance
P-Channel Current-Limit
Threshold
P-Channel Pulse-Skipping
Current Threshold
N-Channel Current-Limit
Threshold
R
OUT
I
REF
V
FB
I
FB
g
m
4
_______________________________________________________________________________________
WCDMA Cellular Phone 600mA
Buck Regulators
ELECTRICAL CHARACTERISTICS (continued)
(V
BATT
= 3.6V,
SHDN
= BATT,
SKIP
= SYNC = GND, V
REF
= 1.25V (MAX1820 only),
T
A
= -40°C to +85°C,
unless otherwise noted.)
(Notes 2, 3)
PARAMETER
LX Leakage Current
Maximum Duty Cycle
Minimum Duty Cycle
SYNC AND OSCILLATOR
SYNC Divide Ratio
(MAX1820X)
SYNC Capture Range
(MAX1820X)
SYNC Divide Ratio
(MAX1820Y)
SYNC Capture Range
(MAX1820Y)
SYNC Leakage Current
Internal Oscillator Frequency
(MAX1820Z, MAX1821)
LOGIC INPUTS (SKIP,
SHDN)
Logic Input High
Logic Input Low
Logic Input Current
V
IH
V
IL
1.6
0.4
1
V
V
µA
I
SYNC
SYNC = sine wave, SYNC input = 200mV
P-P
SYNC = sine wave, SYNC input = 800mV
P-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mV
P-P
SYNC = sine wave, SYNC input = 200mV
P-P
SYNC = sine wave, SYNC input = 800mV
P-P
SYNC = sine wave, AC-coupled,
SYNC input = 500mV
P-P
V
SYNC
= IV (MAX1820Z, MAX1821)
V
SYNC
= IV (MAX1820X, MAX1820Y, and
MAX1821X)
SYNC = GND
13
13
10
18
18
15
-1
-5
0.8
13
13
16
18
18
21
+1
+5
1.2
µA
Hz/Hz
MHz
Hz/Hz
MHz
SYMBOL
I
LX
duty
MAX
duty
MIN
SKIP
= GND
SKIP
= BATT, V
BATT
= 4.2V
CONDITIONS
V
BATT
= 5.5V, LX = GND or BATT
MIN
-1
100
0
10
MAX
1
UNITS
µA
%
%
MAX1820/MAX1821
f
OSC
MHz
Note 2:
Limits are 100% production tested at T
A
= +25°C for UCSP parts. Limits over the entire operating temperature range are
guaranteed by design and characterization but are not production tested.
Note 3:
Specifications to -40°C are guaranteed by design and not subject to production test.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT VOLTAGE
(NORMAL MODE, V
IN
= 3.6V)
MAX1820/21 toc01
EFFICIENCY vs. OUTPUT VOLTAGE
(PWM MODE, V
IN
= 3.6V)
R
LOAD
= 5Ω
90
EFFICIENCY (%)
80
70
60
50
40
R
LOAD
= 10Ω
EFFICIENCY (%)
R
LOAD
= 15Ω
MAX1820/21 toc02
EFFICIENCY vs. INPUT VOLTAGE
NORMAL MODE, R
LOAD
= 10Ω
90
80
70
60
50
40
30
20
10
V
OUT
= 0.4V
V
OUT
= 1.8V
V
OUT
= 3.4V
MAX1820/21 toc03
100
R
LOAD
= 5Ω
90
EFFICIENCY (%)
80
70
60
50
40
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
R
LOAD
= 10Ω
R
LOAD
= 15Ω
100
100
0
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
2.0
2.5
3.0
3.5
4.0
V
IN
(V)
4.5
5.0
5.5
6.0
OUTPUT VOLTAGE (V)
4.0
OUTPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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