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.
________________________Applications
WCDMA Cell Phone Power Amplifiers
PDA, Palmtop, and Notebook Computers
Microprocessor Core Supplies
Digital Cameras
PCMCIA and Network Cards
Hand-Held Instruments
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 RDC
of External Inductor)
♦µMAX or UCSP Packaging
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
________________________________________________________________ Maxim Integrated Products 1
19-2011; Rev 3; 4/05
EVALUATION KIT
AVAILABLE
Ordering Information
PART SYNC
FREQ (MHz) OUTPUT VOLTAGE TEMP RANGE PIN-PACKAGE UCSP MARK
MAX1820ZEBC* No Sync Dynamic -40°C to +85°C 3 ✕ 4 UCSP AAB
MAX1820YEBC* 19.8 Dynamic -40°C to +85°C 3 ✕ 4 UCSP AAL
MAX1820XEBC* 13 Dynamic -40°C to +85°C 3 ✕ 4 UCSP AAM
MAX1820ZEUB No Sync Dynamic -40°C to +85°C 10 µMAX —
MAX1820YEUB 19.8 Dynamic -40°C to +85°C 10 µMAX —
MAX1820XEUB 13 Dynamic -40°C to +85°C 10 µMAX —
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.
Pin Configurations appear at end of data sheet.
Typical Operating Circuits continued at end of data sheet.
SYNC
GND
SHDN
BATT
PGND
COMP
VOUT CONTROL
DAC REF
LX
OUT
13MHz
OR
19.8MHz
MAX1820
SKIP
4.7µH
4.7µF
INPUT
2.6V TO
5.5V
DYNAMIC
OUTPUT
0.4V TO 3.4V
Typical Operating Circuits
*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.
UCSP is a trademark of Maxim Integrated Products, Inc.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Ordering Information continued at end of data sheet.
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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, 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 (VBATT + 0.3V)
Output Short-Circuit Duration ............................................Infinite
Continuous Power Dissipation (TA= +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
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Input BATT Voltage VIN 2.6 5.5 V
Undervoltage Lockout
Threshold VUVLO VBATT rising, 1% hysteresis 2.20 2.35 2.55 V
SKIP = GND (MAX1820Z/MAX1821) 180 300
SKIP = BATT, no switching 450 2000
SKIP = GND (MAX1820Y, MAX1820X, and
MAX1821X) 240 360
Quiescent Current IQ
SKIP = BATT, 1MHz switching 3300
µA
SKIP = GND 530 1000
Quiescent Current in Dropout SKIP = BATT, no switching 550 1000 µA
Shutdown Supply Current ISHDN SHDN = GND 0.1 6 µA
ERROR AMPLIFIER
VREF = 1.932 ±0.005V, load = 0 to 600mA,
SKIP = BATT or GND 3.33 3.4 3.47
OUT Voltage Accuracy
(MAX1820) VOUT VREF = 0.227 ±0.005V, load = 0 to 30mA,
SKIP = BATT, VBATT ≤ 4.2V 0.35 0.40 0.45
V
OUT Input Resistance
(MAX1820) ROUT 250 400 kΩ
REF Input Current (MAX1820) IREF 0.1 1 µA
FB Voltage Accuracy
(MAX1821) VFB FB = COMP 1.225 1.25 1.275 V
FB Input Current (MAX1821) IFB VFB = 1.4V 0.01 50 nA
Transconductance gm30 50 85 µS
COMP Clamp Low Voltage 0.2 0.45 1.0 V
COMP Clamp High Voltage 2.04 2.15 2.28 V
ELECTRICAL CHARACTERISTICS
(VBATT = 3.6V, SHDN = BATT, SKIP = SYNC = GND, VREF = 1.25V (MAX1820 only), TA= 0°C to +85°C, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 2)
Note 1: For UCSP solder profile information, visit www.maxim-ic.com/1st_pages/UCSP.htm.
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
_______________________________________________________________________________________ 3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CONTROLLER
ILX = 180mA, VBATT = 3.6V 0.15 0.3
P-Channel On-Resistance PRDS ILX = 180mA, VBATT = 2.6V 0.2 Ω
ILX = 180mA, VBATT = 3.6V 0.2 0.35
N-Channel On-Resistance NRDS ILX = 180mA, VBATT = 2.6V 0.3 Ω
Current-Sense Transresistance RCS 0.25 0.50 0.75 V/A
P-Channel Current-Limit
Threshold Duty factor = 100% 0.75 1.2 1.55 A
P-Channel Pulse-Skipping
Current Threshold SKIP = GND 0.04 0.13 0.24 A
SKIP = BATT -1.6 -0.85 -0.45
N-Channel Current-Limit
Threshold SKIP = GND 0.02 0.08 0.14 A
LX Leakage Current ILX VBATT = 5.5V, LX = GND or BATT -1 0.1 1 µA
Maximum Duty Cycle dutyMAX 100 %
SKIP = GND 0
Minimum Duty Cycle dutyMIN SKIP = BATT, VBATT = 4.2VP-P 10 %
SYNC AND OSCILLATOR
S Y N C = si ne w ave, S Y N C i np ut = 200m V
P-P 13 13
SYNC Divide Ratio
(MAX1820X) S Y N C = si ne w ave, S Y N C i np ut = 800m V
P-P 13 13 Hz/Hz
SYNC Capture Range
(MAX1820X)
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P 10 13 16 MHz
VSYNC = 1V (MAX1820Z, MAX1821) -1 +1
SYNC Leakage Current
Frequency ISYNC VSYNC = 1V (MAX1820X, MAX1820Y, and
MAX1821X) -5 +5 µA
S Y N C = si ne w ave, S Y N C i np ut = 200m V
P-P 18 18
SYNC Divide Ratio
(MAX1820Y) S Y N C = si ne w ave, S Y N C i np ut = 800m V
P-P 18 18 Hz/Hz
SYNC Capture Range
(MAX1820Y)
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P 15 19.8 21 MHz
Internal Oscillator Frequency
(MAX1820Z, MAX1821) fOSC SYNC = GND 0.8 1 1.2 MHz
LOGIC INPUTS (SKIP, SHDN)
Logic Input High VIH 1.6 V
Logic Input Low VIL 0.4 V
Logic Input Current -1 0.1 1 µA
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 3.6V, SHDN = BATT, SKIP = SYNC = GND, VREF = 1.25V (MAX1820 only), TA= 0°C to +85°C, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 2)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
4 _______________________________________________________________________________________
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
Input BATT Voltage VIN 2.6 5.5 V
Undervoltage Lockout
Threshold VUVLO VBATT rising, 1% hysteresis 2.15 2.55 V
SKIP = GND (MAX1820Z, MAX1821) 300
SKIP = GND (MAX1820X, MAX1820Y, and
MAX1821X) 360
Quiescent Current IQ
SKIP = BATT, no switching 2000
µA
SKIP = GND 1000
Quiescent Current in Dropout SKIP = BATT, no switching 1000 µA
Shutdown Supply Current ISHDN SHDN = GND 6 µA
ERROR AMPLIFIER
VREF = 1.932 ±0.005V, load = 0 to 600mA,
SKIP = BATT or GND 3.33 3.47
OUT Voltage Accuracy
(MAX1820) VOUT VREF = 0.227 ±0.005V, load = 0 to 30mA,
SKIP = BATT, VBATT ≤ 4.2V 0.35 0.45
V
OUT Input Resistance
(MAX1820) ROUT 250 kΩ
REF Input Current (MAX1820) IREF 1µA
FB Voltage Accuracy
(MAX1821) VFB FB = COMP 1.225 1.275 V
FB Input Current (MAX1821) IFB VFB = 1.4V 50 nA
Transconductance gm30 85 µS
COMP Clamp Low Voltage 0.2 1.0 V
COMP Clamp High Voltage 2.04 2.28 V
CONTROLLER
P-Channel On-Resistance PRDS ILX = 180mA, VBATT = 3.6V 0.3 Ω
N-Channel On-Resistance NRDS ILX = 180mA, VBATT = 3.6V 0.35 Ω
Current-Sense Transresistance RCS 0.25 0.75 V/A
P-Channel Current-Limit
Threshold Duty factor = 100% 0.75 1.55 A
P-Channel Pulse-Skipping
Current Threshold SKIP = GND 0.04 0.24 A
SKIP = BATT -1.6 -0.45
N-Channel Current-Limit
Threshold SKIP = GND 0.01 0.14 A
ELECTRICAL CHARACTERISTICS
(VBATT = 3.6V, SHDN = BATT, SKIP = SYNC = GND, VREF = 1.25V (MAX1820 only), TA = -40°C to +85°C, unless otherwise noted.)
(Notes 2, 3)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
_______________________________________________________________________________________ 5
Note 2: Limits are 100% production tested at TA= +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.
PARAMETER SYMBOL CONDITIONS MIN MAX UNITS
LX Leakage Current ILX VBATT = 5.5V, LX = GND or BATT -1 1 µA
Maximum Duty Cycle dutyMAX 100 %
SKIP = GND 0
Minimum Duty Cycle dutyMIN SKIP = BATT, VBATT = 4.2V 10 %
SYNC AND OSCILLATOR
S Y N C = si ne w ave, S Y N C i np ut = 200m V
P-P 13 13
SYNC Divide Ratio
(MAX1820X) S Y N C = si ne w ave, S Y N C i np ut = 800m V
P-P 13 13 Hz/Hz
SYNC Capture Range
(MAX1820X)
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P 10 16 MHz
S Y N C = si ne w ave, S Y N C i np ut = 200m V
P-P 18 18
SYNC Divide Ratio
(MAX1820Y) S Y N C = si ne w ave, S Y N C i np ut = 800m V
P-P 18 18 Hz/Hz
SYNC Capture Range
(MAX1820Y)
SYNC = sine wave, AC-coupled,
SYNC input = 500mVP-P 15 21 MHz
V
SYNC = IV ( M AX 1820Z , M AX 1821) -1 +1
SYNC Leakage Current ISYNC V
SYNC = IV ( M AX 1820X , M AX 1820Y , and
M AX 1821X ) -5 +5 µA
Internal Oscillator Frequency
(MAX1820Z, MAX1821) fOSC SYNC = GND 0.8 1.2 MHz
LOGIC INPUTS (SKIP, SHDN)
Logic Input High VIH 1.6 V
Logic Input Low VIL 0.4 V
Logic Input Current 1µA
ELECTRICAL CHARACTERISTICS (continued)
(VBATT = 3.6V, SHDN = BATT, SKIP = SYNC = GND, VREF = 1.25V (MAX1820 only), TA = -40°C to +85°C, unless otherwise noted.)
(Notes 2, 3)
40
50
60
70
80
90
100
01.00.5 1.5 2.0 2.5 3.0 3.5 4.0
EFFICIENCY vs. OUTPUT VOLTAGE
(NORMAL MODE, VIN = 3.6V)
MAX1820/21 toc01
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
RLOAD = 10Ω
RLOAD = 15Ω
RLOAD = 5Ω
40
50
60
70
80
90
100
01.00.5 1.5 2.0 2.5 3.0 3.5 4.0
EFFICIENCY vs. OUTPUT VOLTAGE
(PWM MODE, VIN = 3.6V)
MAX1820/21 toc02
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
RLOAD = 10Ω
RLOAD = 15Ω
RLOAD = 5Ω
0
20
10
40
30
60
50
70
90
80
100
2.0 3.0 3.52.5 4.0 4.5 5.0 5.5 6.0
MAX1820/21 toc03
VIN (V)
EFFICIENCY (%)
EFFICIENCY vs. INPUT VOLTAGE
NORMAL MODE, RLOAD = 10Ω
VOUT = 1.8V VOUT = 3.4V
VOUT = 0.4V
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
90
0
1 100010010
MAX1821 EFFICIENCY vs. LOAD CURRENT
(VOUT = 3.3V)
30
10
70
50
100
40
20
80
60
MAX1820/21 toc04
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.6V
VIN = 5.0V
SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)
VIN = 3.6V
90
0
1 100010010
MAX1821 EFFICIENCY vs. LOAD CURRENT
(VOUT = 2.5V)
30
10
70
50
100
40
20
80
60
MAX1820/21 toc05
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.6V
VIN = 3.6V
VIN = 5.0V
SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)
VIN = 2.7V
VIN = 2.7V
90
0
1 100010010
MAX1821 EFFICIENCY vs. LOAD CURRENT
(VOUT = 1.5V)
30
10
70
50
100
40
20
80
60
MAX1820/21 toc06
LOAD CURRENT (mA)
EFFICIENCY (%)
VIN = 5.0V
VIN = 3.6V
SKIP = GND (DASHED LINE)
SKIP = BATT (SOLID LINE)
VIN = 2.7V
0
40
20
80
60
120
100
140
0 200 300100 400 500 600
DROPOUT VOLTAGE vs. LOAD CURRENT
MAX1820/21 toc07
LOAD CURRENT (mA)
DROPOUT VOLTAGE (mV)
VOUT = 3.4V
RL = 57mΩ
0
2
1
5
4
3
8
7
6
9
2.0 3.0 3.52.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1820/21 toc08
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
VOUT = 1.5V
SKIP = BATT
20
80
60
40
120
100
200
180
160
140
220
2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1820/21 toc09
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
VOUT = 1.5V
SKIP = GND
MAX1820/21 toc10
B
C
A
400ns/div
A: VLX, 5V/div
B: INDUCTOR CURRENT, 500mA/div
C: VOUT (AC-COUPLED), 5mV/div
HEAVY-LOAD SWITCHING WAVEFORMS
(VIN = 3.8V, VOUT = 3.4V,
ILOAD = 600mA, SKIP = BATT)
MAX1820/21 toc11
B
C
A
400ns/div
A: VLX, 5V/div
B: INDUCTOR CURRENT, 500mA/div
C: VOUT (AC-COUPLED), 5mV/div
MEDIUM-LOAD SWITCHING WAVEFORMS
(VIN = 3.8V, VOUT = 1.8V,
ILOAD = 300mA, SKIP = BATT)
MAX1820/21 toc12
B
C
A
400ns/div
A: VLX, 5V/div
B: INDUCTOR CURRENT, 100mA/div
C: VOUT (AC-COUPLED), 5mV/div
LIGHT-LOAD PWM SWITCHING WAVEFORMS
(VIN = 3.8V, VOUT = 0.45V,
ILOAD = 30mA, SKIP = BATT)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
_______________________________________________________________________________________ 7
MAX1820/21 toc13
B
C
A
2µs/div
A: VLX, 5V/div
B: INDUCTOR CURRENT, 500mA/div
C: VOUT (AC-COUPLED), 20mV/div
LIGHT-LOAD SKIP-SWITCHING WAVEFORMS
(VIN = 4.2V, VOUT = 1.5V,
LOAD = 30mA, SKIP = GND)
MAX1820/21 toc14
2ms/div
EXITING AND ENTERING SHUTDOWN
(VIN = 3.6V, VOUT = 3.4V, RLOAD = 15Ω)
VOUT
2V/div
IBATT
0.5A/div
VSHDN
5V/div
MAX1820/21 toc15
40µs/div
LOAD TRANSIENT (ILOAD = 20mA TO 420mA,
VOUT = 1.5V, VIN = 3.6V, SKIP = BATT)
IOUT
200mA/div
VOUT
AC-COUPLED
100mV/div
COUT = 10µF
MAX1820/21 toc16
40µs/div
LOAD TRANSIENT (ILOAD = 20mA TO 420mA,
VOUT = 1.5V, VIN = 3.6V, SKIP = GND)
IOUT
200mA/div
VOUT
AC-COUPLED
100mV/div
COUT = 10µF
MAX1820/21 toc17
20µs/div
MAX1820
REF TRANSIENT (VREF = 0.23V TO 1.932V,
RLOAD = 10Ω, VIN = 3.6V, SKIP = BATT)
VREF
1V/div
VOUT
1V/div
MAX1820/21 toc18
40µs/div
LINE TRANSIENT (VIN = 3.6V TO 4.0V,
VOUT = 1.5V, ILOAD = 300mA)
VIN
200mV/div
VOUT
AC-COUPLED
20mV/div
COUT = 10µF
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
8 _______________________________________________________________________________________
0.1 1 10
OUTPUT SWITCHING HARMONICS
vs. FREQUENCY
(VIN = 3.8V, VOUT = 3.4V, ILOAD = 600mA)
MAX1820/21 toc19
FREQUENCY (MHz)
HARMONICS (mVRMS)
1.6
1.2
0.8
0.4
0
0.1 1 10
OUTPUT SWITCHING HARMONICS
vs. FREQUENCY
(VIN = 3.8V, VOUT = 1.8V, ILOAD = 300mA)
MAX1820/21 toc20
FREQUENCY (MHz)
HARMONICS (mVRMS)
0
0.8
0.4
1.6
1.2
Pin Description
PIN
MAX1820
UCSP
MAX1820
µMAX
MAX1821
UCSP
MAX1821
µMAX
NAME FUNCTION
A1 1 A1 1 SKIP
PWM/Skip-Mode Input. Drive with logic 0 to use PWM at medium
and heavy loads and pulse skipping at light loads. Drive with
logic 1 to force PWM at all loads.
A2 2 A2 2 COMP
Compensation. Typically, connect an 82kΩ (for MAX1821) or
43kΩ (for MAX1820) series resistor and 330pF capacitor from
this pin to GND to stabilize the regulator.
A3 3 — — OUT Output Voltage Sense Input. Connect OUT directly to the output.
0.1 1 10
OUTPUT SWITCHING HARMONICS
vs. FREQUENCY
(VIN = 4.2V, VOUT = 0.4V, ILOAD = 30mA)
MAX1820/21 toc21
FREQUENCY (MHz)
HARMONICS (mVRMS)
0
0.8
0.4
1.6
1.2
FREQUENCY (MHz)
OUTPUT NOISE (VIN = 3.6V,
VOUT = 1.8V, IOUT = 300mA)
4.0
3.0
1.0
2.0
MAX1820/21 toc22
0
0.1 1 10 100 250
NOISE (µV/√Hz)
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
_______________________________________________________________________________________ 9
_______________Detailed Description
The MAX1820/MAX1821 PWM step-down DC-DC con-
verters are optimized for low-voltage, battery-powered
applications where high efficiency and small size are
priorities. The MAX1821 is a general-purpose device
that uses external feedback resistors to set the output
voltage from 1.25V to VBATT, and the MAX1820 is
specifically intended to power a linear PA in WCDMA
handsets. An analog control signal dynamically adjusts
the MAX1820’s output voltage from 0.4V to 3.4V with a
settling time <30µs.
The MAX1820/MAX1821 operate at a high 1MHz
switching frequency that reduces external component
size. Each device includes an internal synchronous rec-
tifier that provides for high efficiency and eliminates the
need for an external Schottky diode. The normal operat-
ing mode uses constant-frequency PWM switching at
medium and heavy loads, and automatically pulse
skips at light loads to reduce supply current and extend
battery life. An additional forced PWM mode (with
optional external synchronization) switches at a con-
stant frequency, regardless of load, to provide a well-
controlled spectrum in noise-sensitive applications.
Battery life is maximized by low-dropout operation at
100% duty-cycle and a 0.1µA (typ) logic-controlled
shutdown mode.
PWM Control
The MAX1820/MAX1821 use a slope-compensated,
current-mode PWM controller capable of achieving
100% duty cycle. The current-mode control design is
capable of minimum duty cycles of less than 10%,
ensuring a constant switching frequency with outputs
as low as 0.4V when powered from a single lithium-ion
(Li+) cell. Current-mode feedback provides stable
switching and cycle-by-cycle current limiting for superi-
or load and line response and protection of the internal
MOSFET and synchronous rectifier. The output voltage
is regulated by switching at a constant frequency and
then modulating the power transferred to the load dur-
Pin Description (continued)
PIN
MAX1820
UCSP
MAX1820
µMAX
MAX1821
UCSP
MAX1821
µMAX
NAME FUNCTION
— — A3 3 FB
Output Feedback Sense Input. To set the output voltage,
connect FB to the center of an external resistive divider between
the output and GND. FB voltage regulates to 1.25V.
A4 4 — — REF
External Reference Input. Connect REF to the output of a D/A
converter for dynamic adjustment of the output voltage. REF-to-
OUT gain is 1.76.
— — A4 4 REF Internal Reference Bypass. Connect a 0.047µF capacitor from
REF to GND.
B4 5 B4 5 GND Ground
C4 6 C4 6 PGND Power Ground
C3 7 C3 7 LX Inductor Connection. LX connects to the drains of the internal
power MOSFETs. LX is high impedance in shutdown mode.
C2 8 C2 8 BATT Supply Voltage Input. Connect BATT to a 2.6V to 5.5V source.
Bypass BATT to PGND with a low-ESR 10µF capacitor.
C1 9 C1 9 SHDN Active-Low, Shutdown Control Input
B1 10 B1 10 SYNC
Clock Synchronization Input. Drive SYNC with a 13MHz
(MAX1820X, MAX1821X) or 19.8MHz (MAX1820Y) AC-coupled
sine-wave input to synchronize power switching at 1MHz.
MAX1820Z and MAX1821 do not have SYNC capability.
Connect SYNC to GND to use the internally generated,
free-running 1MHz clock. MAX1820Z and MAX1821 SYNC pin
must be connected to GND.
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
10 ______________________________________________________________________________________
ing each cycle, using the PWM comparator. The power
transferred to the load is adjusted by changes in the
inductor peak current limit during the first half of each
cycle, based on the output error voltage.
A new cycle begins at each falling edge of the internal
oscillator. The controller turns on the P-channel MOS-
FET to increase the inductor current, and the slope
compensation block initiates a new reference current
ramp that is summed with the internal P-channel MOS-
FET current (Figures 1 and 2).
The second half of the cycle begins when the reference
ramp is greater than the error voltage. The P-channel
MOSFET is turned off, the synchronous rectifier is
turned on, and inductor current continues to flow to the
output capacitor. The output capacitor stores charge
when the current is high and releases it when the
inductor current is low, smoothing the voltage across
VOLTAGE
REFERENCE
PWM CONTROL
AND
SKIP LOGIC
ERROR SIGNAL
SLOPE COMP
CURRENT SENSE
SKIP THRESHOLD
TRANSIMPEDANCE
ERROR AMP
MAX1820
SKIP
COMPARATOR
PWM
COMPARATOR
LX
PGND
÷13 OR
÷18
1.25V TO
IC BIAS
0.45V TO 2.15V
1MHz
OSCILLATOR
CLAMP
COMP
SYNC
SKIP
SHDN
GND
BATT
OUT
REF
Figure 1. MAX1820 Simplified Functional Diagram (No SYNC for MAX1820Z)
VOLTAGE
REFERENCE
PWM CONTROL
AND
SKIP LOGIC
ERROR SIGNAL
SLOPE COMP
CURRENT SENSE
SKIP THRESHOLD
TRANSIMPEDANCE
ERROR AMP
MAX1821
SKIP
COMPARATOR
PWM
COMPARATOR
LX
PGND
1.25V TO
IC BIAS
0.45V TO 2.15V
1MHz
OSCILLATOR
CLAMP
COMP
SYNC
SKIP
SHDN
GND
BATT
OUT
REF
Figure 2. MAX1821 Simplified Functional Diagram (No SYNC for MAX1821)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
______________________________________________________________________________________ 11
the load. The duty cycle of a buck step-down converter
is ideally a ratio of the output voltage to input voltage in
steady-state condition.
The MAX1820/MAX1821 have internal switch current
limits of 1.2A (typ). If ILX exceeds this maximum, the
high-side FET turns off and the synchronous rectifier
turns on. This lowers the duty cycle and causes the out-
put voltage to droop as long as the load current
remains excessive. There is also a synchronous rectifier
current limit of -0.85A when the device is operating in
forced PWM mode (see the Forced PWM Operation sec-
tion). If the negative current limit is exceeded, the syn-
chronus rectifier is turned off, and the inductor current
continues to flow through its body diode until the begin-
ning of the next cycle or the inductor current drops to
zero. This means there is a limit on how much current
the device is allowed to shuttle in response to output
power reduction.
Normal Mode Operation
Connecting SKIP to GND enables MAX1820/MAX1821
normal operation (Figure 3). This allows automatic PWM
control at medium and heavy loads and skip mode at
light loads to improve efficiency and reduce quiescent
current to 180µA. Operating in normal mode also allows
the MAX1820/MAX1821 to pulse skip when the peak
inductor current drops below 130mA, corresponding to
a load current of approximately 65mA.
During skip operation, the MAX1820/MAX1821 switch
only as needed to service the load, reducing the
switching frequency and associated losses in the inter-
nal switch, the synchronous rectifier, and the external
inductor.
There are three steady-state operating conditions for
the MAX1820/MAX1821 in normal mode. The device
performs in continuous conduction for heavy loads in a
manner identical to forced PWM mode. The inductor
current becomes discontinuous at medium loads,
requiring the synchronous rectifier to be turned off
before the end of a cycle as the inductor current reach-
es zero. The device enters into skip mode when the
converter output voltage exceeds its regulation limit
before the inductor current reaches its skip thres-
hold level.
During skip mode, a switching cycle initiates when the
output voltage has dropped out of regulation. The P-
channel MOSFET switch turns on and conducts current
to the output-filter capacitor and load until the inductor
current reaches the skip peak current limit. Then the
main switch turns off, and the magnetic field in the
inductor collapses, while current flows through the syn-
chronous rectifier to the output filter capacitor and the
load. The synchronous rectifier is turned off when the
inductor current reaches zero. The MAX1820/ MAX1821
wait until the skip comparator senses a low output volt-
age again.
Forced PWM Operation
Connect SKIP to BATT for forced PWM operation.
Forced PWM operation is desirable in sensitive RF and
data-acquisition applications to ensure that switching
harmonics do not interfere with sensitive IF and data-
sampling frequencies. A minimum load is not required
during forced PWM operation since the synchronous
rectifier passes reverse-inductor current as needed to
allow constant-frequency operation with no load.
BATT LX
PGND
FB
COMP
SYNC
REF
SKIP GND
SHDN R1
6kΩ
RC
82kΩ
C1
330pF
R2
30kΩ
4.7µH
4.7µF
0.047µF
VIN = 2.6V TO 5.5V
* CAN BE OMITTED IF CERAMIC OUTPUT CAPACITOR IS USED.
VOUT = 1.5V
C2*
1pF
MAX1821
10µF0.1µF
Figure 3. Standard Operating Circuit
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
12 ______________________________________________________________________________________
Forced PWM operation uses higher supply current with
no load (3.3mA typ) compared to skip mode.
100% Duty-Cycle Operation
The on-time can exceed one internal oscillator cycle,
which permits operation up to 100% duty cycle. As the
input voltage drops, the duty cycle increases until the
P-channel MOSFET is held on continuously. Dropout
voltage in 100% duty cycle is the output current multi-
plied by the on-resistance of the internal switch and
inductor, approximately 150mV (IOUT = 600mA). Near
dropout, the on-time may exceed one PWM clock
cycle; therefore, small-amplitude subharmonic ripple
may occur.
COMP Clamp
The MAX1820/MAX1821 compensation network has a
0.45V to 2.15V error regulation range. The clamp pre-
vents COMP from rising too high or falling too low to
optimize transient response.
Dropout
Dropout occurs when the input voltage is less than the
desired output voltage plus the IR drops in the circuit
components. The duty cycle is 100% during this condi-
tion, and the main switch remains on, continuously
delivering current to the output up to the current limit.
IR drops in the circuit are primarily caused by the on-
resistance of the main switch and the resistance in the
inductor.
During dropout, the high-side P-channel MOSFET turns
on, and the controller enters a low-current consumption
mode. Every 6µs (6 cycles), the MAX1820/MAX1821
check to see if the device is still in dropout. The device
remains in this mode until the MAX1820/MAX1821 are
no longer in dropout.
Undervoltage Lockout (UVLO)
The MAX1820/MAX1821 do not operate with battery
voltages below the UVLO threshold of 2.35V (typ). The
BATT input remains high impedance until the supply
voltage exceeds the UVLO threshold. This guarantees
the integrity of the output voltage regulation and pre-
vents excessive current during startup and as the bat-
tery supply voltage drops during usage.
Synchronous Rectification
An N-channel synchronous rectifier eliminates the need
for an external Schottky diode and improves efficiency.
The synchronous rectifier turns on during the second
half of each cycle (off-time). During this time, the volt-
age across the inductor is reversed, and the inductor
current falls. In normal mode, the synchronous rectifier
is turned off when either the output falls out of regula-
tion (and another on-time begins) or when the inductor
current approaches zero. In forced PWM mode, the
synchronous rectifier remains active until the beginning
of a new cycle.
SYNC Input and Frequency Control
The MAX1820Z and MAX1821 internal oscillator is set
to a fixed 1MHz switching frequency. The MAX1820Z
and MAX1821 do not have synchronizing capability
and the SYNC pin must be connected to GND. The
MAX1820Y, MAX1820X, and MAX1821X are capable of
synchronizing to external signals. For external synchro-
nization, drive the SYNC pin with a 13MHz (MAX1820X
and MAX1821X) or 19.8MHz (MAX1820Y) AC-coupled
sine wave. SYNC has a perfect 13:1 (MAX1820X and
MAX1821X) or 18:1 (MAX1820Y) clock divider for 1MHz
(MAX1820X and MAX1821X) or 1.1MHz (MAX1820Y)
switching from common system clocks. The input fre-
quency range for SYNC is 10MHz to 16MHz
(MAX1820X, MAX1821X) or 15MHz to 21MHz
(MAX1820Y). Connect SYNC to GND to use the internal
free-running oscillator at 1MHz.
Shutdown Mode
Drive SHDN to GND to place the MAX1820/MAX1821 in
shutdown mode. In shutdown, the reference, control
circuitry, internal switching MOSFET, and the synchro-
nous rectifier turn off, reducing the supply current to
0.1µA, and the output goes high impedance. Connect
SHDN to BATT for normal operation.
Current-Sense Comparators
The MAX1820/MAX1821 use several internal current-
sense comparators. In PWM operation, the PWM com-
parator terminates the cycle-by-cycle on-time (Figures
1 and 2) and provides improved load and line
response. This allows tighter specification of the induc-
tor-saturation current limit to reduce inductor cost. A
second current-sense comparator used across the P-
channel switch controls entry into skip mode. A third
current-sense comparator monitors current through the
internal N-channel MOSFET to prevent excessive
reverse currents and determine when to turn off the
synchronous rectifier. A fourth comparator used at the
P-channel MOSFET detects overcurrent. This protects
the system, external components, and internal
MOSFETs under overload conditions.
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
______________________________________________________________________________________ 13
Applications Information
Setting the Output Voltage (MAX1820)
The MAX1820 is optimized for highest system efficiency
when applying power to a linear PA in WCDMA hand-
sets. When transmitting at less than full power, the sup-
ply voltage to the PA is reduced (from 3.4V to as low as
0.4V) to greatly reduce battery current. Figure 4 shows
the typical WCDMA PA load profile. The use of a DC-
DC converter such as the MAX1820 dramatically
reduces battery drain in these applications.
The MAX1820’s output voltage is dynamically
adjustable from 0.4V to VBATT by the use of the REF
input. The gain from VREF to VOUT is internally set to
1.76. VOUT can be adjusted during operation by driving
REF with an external DAC. The MAX1820 output
responds to full-scale change in voltage and current in
<30µs.
Setting the Output Voltage (MAX1821)
The MAX1821 is intended for general-purpose step-
down applications where high efficiency is a priority.
Select an output voltage between 1.25V and VBATT by
connecting FB to a resistive divider between the output
and GND (Figure 3). Select feedback resistor R2 in the
5kΩto 30kΩrange. R1 is then given by:
where VFB = 1.25V.
Compensation and Stability
The MAX1820/MAX1821 are externally compensated
by placing a resistor and a capacitor (RCand C1) in
series, from COMP to GND (Figure 3). The capacitor
integrates the current from the transimpedance amplifi-
er, averaging output capacitor ripple. This sets the
device speed for transient responses and allows the
use of small ceramic output capacitors because the
phase-shifted capacitor ripple does not disturb the cur-
rent regulation loop. The resistor sets the proportional
gain of the output error voltage by a factor gm✕RC.
Increasing this resistor also increases the sensitivity of
the control loop to the output capacitor ripple.
This resistor and capacitor set a compensation zero
that defines the system’s transient response. The load
pole is a dynamic pole, shifting the pole frequency with
changes in load. As the load decreases, the pole fre-
quency shifts to the left. System stability requires that
the compensation zero must be placed properly to
ensure adequate phase margin (at least 30° at unity
gain). The following is a design procedure for the com-
pensation network:
1) Select an appropriate converter bandwidth (fC) to
stabilize the system while maximizing transient
response. This bandwidth should not exceed 1/5 of
the switching frequency. Use 100kHz as a reason-
able starting point.
2) Calculate the compensation capacitor, C1, based
on this bandwidth:
Resistors R1 and R2 are internal to the MAX1820; use
R1 = 151kΩand R2 = 199kΩas nominal values for cal-
culations. These resistors are external to the MAX1821
(see the Setting the Output Voltage section). Using
VOMAX = 3.4V, IOMAX = 0.6A, gm= 50µs, RCS = 0.75Ω,
C1 is evaluated as:
TION 3
Selecting the nearest standard value of 330pF corre-
sponds to a 103kHz bandwidth, which is still accept-
able per the above criteria.
C1 3.4V
0.6A
1
050 s 1
151k +199k
1
23 = 341pF
=⎛
⎝
⎜⎞
⎠
⎟⎛
⎝
⎜⎞
⎠
⎟×
⎛
⎝
⎜⎞
⎠
⎟
×××
⎛
⎝
⎜⎞
⎠
⎟
.
.
75
99
14 100
Ω
Ω
ΩΩ
µk
kHz
C1 V
I
1
RgR2
R1+R2
1
2
O(MAX)
O(MAX) CS mC
=⎛
⎝
⎜⎞
⎠
⎟⎛
⎝
⎜⎞
⎠
⎟×
⎛
⎝
⎜⎞
⎠
⎟××
⎛
⎝
⎜⎞
⎠
⎟
πf
R1
V
V-
OUT
FB
=⎛
⎝
⎜⎞
⎠
⎟
R2 1
30 600
WCDMA PA SUPPLY CURRENT (mA)
300
0.4
1.0
3.0
3.4
WCDMA PA SUPPLY VOLTAGE (V)
Figure 4. Typical WCDMA PA Load Profile
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
14 ______________________________________________________________________________________
3) Calculate the equivalent load impedance, RL, by:
4) Calculate the compensation resistance (RC) value to
cancel out the dominant pole created by the output
load and the output capacitance:
Solving for RCgives:
5) Calculate the high-frequency compensation pole to
cancel the zero created by the output capacitor’s
equivalent series resistance (ESR):
Solving for C2 gives:
In this case, C2 can be omitted due to the use of
ceramic capacitors. Larger output capacitors and high-
er ESR may require the use of capacitor C2.
Inductor Selection
A 4µH to 6µH inductor with a saturation current of at
least 800mA is recommended for most applications.
For best efficiency, the inductor’s DC resistance should
be <200mΩ, and saturation current should be >1A. See
Table 1 for recommended inductors and manufacturers.
For most designs, a reasonable inductor value (LIDEAL)
can be derived from the following equation:
where LIR is the inductor current ripple as a percentage.
LIR should be kept between 20% and 40% of the maxi-
mum load current for best performance and stability.
The maximum inductor current is:
The inductor current becomes discontinuous if IOUT
decreases to LIR/2 from the output current value used
to determine LIDEAL.
Input Capacitor Selection
The input capacitor reduces the current peaks drawn
from the battery or input power source and reduces
switching noise in the IC. The impedance of the input
capacitor at the switching frequency should be less
than that of the input source so high-frequency switch-
ing currents do not pass through the input source.
The input capacitor must meet the ripple-current
requirement (IRMS) imposed by the switching currents.
Nontantalum chemistries (ceramic, POSCAP, or OS-
CON) are preferred due to their resistance to power-up
surge currents:
For optimal circuit reliability, choose a capacitor that
has less than 10°C temperature rise at the peak ripple
current.
IV(V -V)
V
RMS LOAD
OUT BATT OUT
BATT
=⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
I
II
L(MAX) OUT(MAX)
=+
⎛
⎝
⎜⎞
⎠
⎟
12
LIR
LV(V -V)
V
IDEAL OUT BATT OUT
BATT OUT(MAX) OSC
=×× ×ƒLIR I
CRC
Rk
pF2 3
001
80 8 055=×=×=
ESR OUT 4.7 Fµ.
..
Ω
Ω
1
2
1
2
ESR OUT
×× × =×× ×ππRC RC32
`
RCR
C1
3.4V
0.6A
4.7 = 80.8k
L OUT
=×=⎛
⎝
⎜⎞
⎠
⎟⎛
⎝
⎜⎞
⎠
⎟
CF
pF
µ
330 Ω
1
2
1
2
L OUT C
×× × =×× ×ππRC R C1
RL
V
I
OUT(MAX)
OUT(MAX)
≈
Table 1. Suggested Inductors
MANUFACTURER PART NUMBER INDUCTANCE
(µH) ESR (mΩ)SATURATION
CURRENT (A)
DIMENSIONS
(mm)
Coilcraft DO1606 4.7 120 1.2 5.3 ✕ 5.3 ✕ 2.0
Coilcraft LPT1606-472 4.7 240 (max) 1.2 6.5 ✕ 5.3 ✕ 2.0
Sumida CDRH4D18-4R7 4.7 125 0.84 5 ✕ 5 ✕ 2
Sumida CR43 4.7 108.7 1.15 4.5 ✕ 4.0 ✕ 3.5
Sumida CDRH5D18-4R1 4.1 57 1.95 5.5 ✕ 5.5 ✕ 2.0
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
______________________________________________________________________________________ 15
Output Capacitor Selection
The output capacitor is required to keep the output volt-
age ripple small and to ensure regulation control loop
stability. The output capacitor must have low imped-
ance at the switching frequency. Ceramic capacitors
are recommended. The output ripple is approximately:
VRIPPLE ≈LIR ✕IOUT(MAX)
See the Compensation Design section for a discussion
of the influence of output capacitance and ESR on reg-
ulation control-loop stability.
The capacitor voltage rating must exceed the maximum
applied capacitor voltage. Consult the manufacturer’s
specifications for proper capacitor derating. Avoid Y5V
and Z5U dielectric types due to their huge voltage and
temperature coefficients of capacitance and ESR.
PC Board Layout and Routing
High switching frequencies and large peak currents
make PC board layout a very important part of design.
Good design minimizes excessive EMI on the feedback
paths and voltage gradients in the ground plane, both
of which can result in instability or regulation errors.
Connect the inductor, input filter capacitor, and output
filter capacitor as close together as possible, and keep
their traces short, direct, and wide. Connect their
ground pins at a single common node in a star-ground
configuration. The external voltage-feedback network
should be very close to the FB pin, within 0.2in (5mm).
Keep noisy traces (from the LX pin, for example) away
from the voltage-feedback network; also, keep them
separate, using grounded copper. Connect GND and
PGND at a single point, as close as possible to the
MAX1820/MAX1821. The MAX1820/MAX1821 evalua-
tion kit manual illustrates an example PC board layout
and routing scheme.
UCSP Package Consideration
For general UCSP package information and PC layout
considerations, refer to the Maxim Application Note
(Wafer-Level Ultra-Chip-Board-Scale Package).
______________________UCSP Reliability
The chip-scale package (UCSP) represents a unique
packaging form factor that may not perform equally to a
packaged product through traditional mechanical relia-
bility tests. UCSP reliability is integrally linked to the
user’s assembly methods, circuit board material, and
usage environment. The user should closely review
these areas when considering use of a UCSP package.
Performance through Operating Life Test and Moisture
Resistance remains uncompromised as it is primarily
determined by the wafer-fabrication process.
Mechanical stress performance is a greater considera-
tion for a UCSP package. UCSPs are attached through
direct solder contact to the user’s PC board, foregoing
the inherent stress relief of a packaged-product lead
frame. Solder joint contact integrity must be consid-
ered. Information on Maxim’s qualification plan, test
data, and recommendations are detailed in the UCSP
application note, which can be found on Maxim’s website,
www.maxim-ic.com.
____________________Chip Information
TRANSISTOR COUNT: 2722
×+
׃ ×
()
⎡
⎣
⎢
⎢
⎤
⎦
⎥
⎥
ESR C
OSC OUT
1
2
Table 2. Capacitor Selection
CAPACITOR CAPACITOR
VALUE (µF)
ESR
(mΩ)
CAPACITOR
TYPE
CBATT 4.7 to 10 <150 Ceramic
COUT
(MAX1820) 2.2 to 4.7 <50 Ceramic
COUT
(MAX1821) 4.7 to 10 <150 Ceramic
Table 3. Component Manufacturers
MANUFACTURER USA PHONE
NUMBER WEBSITE
Coilcraft 847-639-6400 www.coilcraft.com
Kemet 408-986-0424 www.kemet.com
Panasonic 847-468-5624 w w w .p anasoni c.com
Sumida 847-956-0666 www.sumida.com
Taiyo Yuden 408-573-4150 www.t-yuden.com
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
16 ______________________________________________________________________________________
SYNC
GND
SHDN
BATT
PGND
COMP
REF
LX
FB
MAX1821
SKIP
INPUT
2.6V TO
5.5V
OUTPUT
1.25V TO 5.5V
Typical Operating Circuits (continued)
1
2
3
4
5
10
9
8
7
6
SYNC
BATT
LXREF
( ) ARE FOR MAX1821 ONLY.
OUT (FB)
COMP
SKIP
MAX1820
MAX1821
µMAX
TOP VIEW
PGNDGND
SHDN
COMP OUT (FB)
SYNC
BATT LX
UCSP
TOP VIEW AFTER ASSEMBLED ON PC BOARD (BUMPS AT THE BOTTOM)
( ) ARE FOR MAX1821 ONLY.
A1 A3A2
B1
C1 C2 C3
A
B
C
123
GND
PGND
A4
B4
C4
4
REFSKIP
SHDN
Pin Configurations
Ordering Information (continued)
PART SYNC
FREQ (MHz) OUTPUT VOLTAGE TEMP RANGE PIN-PACKAGE UCSP MARK
MAX1821EBC* No Sync Programmable -40°C to +85°C 3 ✕ 4 UCSP AAC
MAX1821EUB No Sync Programmable -40°C to +85°C 10 µMAX —
MAX1821XEBC* 13 Programmable -40°C to +85°C 3 ✕ 4 UCSP AAV
MAX1821XEUB 13 Programmable -40°C to +85°C 10 µMAX —
*UCSP reliability is integrally linked to the user’s assembly methods, circuit board material, and environment. Refer to the UCSP
Reliability Notice in the UCSP Reliability section for more information.
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
______________________________________________________________________________________ 17
12L, UCSP 4x3.EPS
F1
1
21-0104
PACKAGE OUTLINE, 4x3 UCSP
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
MAX1820/MAX1821
WCDMA Cellular Phone 600mA
Buck Regulators
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
18 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2005 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products, Inc .
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
10LUMAX.EPS
PACKAGE OUTLINE, 10L uMAX/uSOP
1
1
21-0061 I
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
1
0.498 REF
0.0196 REF
S
6°
SIDE VIEW
α
BOTTOM VIEW
0° 0° 6°
0.037 REF
0.0078
MAX
0.006
0.043
0.118
0.120
0.199
0.0275
0.118
0.0106
0.120
0.0197 BSC
INCHES
1
10
L1
0.0035
0.007
e
c
b
0.187
0.0157
0.114
H
L
E2
DIM
0.116
0.114
0.116
0.002
D2
E1
A1
D1
MIN
-A
0.940 REF
0.500 BSC
0.090
0.177
4.75
2.89
0.40
0.200
0.270
5.05
0.70
3.00
MILLIMETERS
0.05
2.89
2.95
2.95
-
MIN
3.00
3.05
0.15
3.05
MAX
1.10
10
0.6±0.1
0.6±0.1
Ø0.50±0.1
H
4X S
e
D2
D1
b
A2 A
E2
E1 L
L1
c
α
GAGE PLANE
A2 0.030 0.037 0.75 0.95
A1
